Atlassino Academy · Slots · Lesson 2

Return to player: twins that aren't

Two machines can carry the same glass, land a prize just as often, and still give back different shares of everything staked — and the share is printed on neither of them.

About 16 minutes
Illustrated hosts: Leo and Maya
Last checked 27 October 2026

Lesson 2 of the slots track. One number, fixed before a machine ever reaches the floor, and how little an evening at that machine has to say about it.

Two machines stand side by side with the same picture on the glass. One has been paying all evening and one has not. Which one do you sit at?

The short answer

Nothing you can see decides it. A return figure counts what a game gives back across its whole working life, and a thousand spins of that life is a rounding error: stand a machine that gives back 85% beside one that gives back 92%, run 1,000 spins on each, and the poorer of the two machines finishes level with the other machine or ahead of it 39 times in a hundred. Neither figure is printed anywhere on the cabinet, and the two machines can match down to how often they land a prize.

Does not move the share that comes back

The cabinet, and how old it is
How bright the screen is
How often the machine lands a prize
What the machine paid ten minutes ago
The figure published for the country

The share that comes back is worked out from these two

What each symbol pays, printed on the paytable where anyone can read it
How many stops on the reel carry each symbol, printed nowhere

Leo and Maya stand in front of two identical gaming cabinets with the same panel art, each of them resting a fingertip on the small empty plate fixed to the front of the machine beside them.

Leo smiling, explaining with an open hand.

Leoformer dealer · rules and maths

What is attached to it is a number set in a factory and checked before the machine came through the door. So: what that number counts, how long it takes to show itself, and what two machines wearing the same picture can be hiding from each other.

What the figure counts

Return to player is a share of the bets, not a share of what is in your pocket. Money goes in, some of it comes back, the same money goes in again, and it keeps going in until nothing is left — so ten bets in front of a machine buy far more than ten spins, and every one of those spins counts in the figure. That is turnover.

A machine that gives back 85%67 spins

A machine that gives back 92%125 spins

Ten bets, one bet a spin, nothing added and nothing taken out. The bars are the same ten bets on two machines, and the only thing that differs between the two bars is the share the machine gives back: what a machine keeps on every spin is what empties the ten bets.

The rate is fixed and the spin is not. Every prize is drawn at random; what was programmed is how often each prize comes up, and those chances were set according to the share the game is built to give back. So 85% describes no evening you will ever sit through, and was never meant to: it describes the working life of the machine — every spin from the day it is switched on to the day it is carted out.

How long it takes to show

A player has one instrument and it is a blunt one: money in against money out. Point it at a machine that gives back 85% and at one that gives back 92%, and it reads like this.

What each machine has actually returned, by length of run
After	The 85% machine has shown	The 92% machine has shown
100 spins	30% to 175%	30% to 180%
1,000 spins	57% to 135%	64% to 143%
10,000 spins	73% to 99%	80% to 106%
1,000,000 spins	84% to 86%	91% to 93%

Nine runs in ten land inside the range shown. Only at 1,000,000 spins do the two ranges come apart, and by then ninety-nine runs in a hundred on the 85% machine sit within 2.1 points of its figure.

Now stand the two machines side by side, run the same number of spins on each, and pick the machine whose counter is higher. The machine that gives back the smaller share finishes level with the other machine or ahead of it this often:

How often the machine that gives back the smaller share ends a run level with the other machine or ahead of it
After	The 85% machine is level or ahead
100 spins	47 in 100
1,000 spins	39 in 100
10,000 spins	27 in 100
100,000 spins	3 in 100

Two machines, one difference

Both machines carry the same glass and the same paytable. Both land a prize on 8.8% of spins. On both, the largest prize sits on 1 in 5,000 spins. Behind each is a reel of ten thousand stops, every stop as likely as any other. Both machines are made up: no manufacturer we could read publishes a real reel strip.

Stops on the reel of each machine, out of ten thousand
Symbol	The 85% machine	The 92% machine
pays 500 times the bet	2	2
pays 100 times	8	8
pays 25 times	60	95
pays 10 times	230	230
pays 5 times	580	545
pays nothing	9,120	9,120

Only two rows differ, and in opposite directions; every other row is identical.

35 stops come off the symbol that pays five times the bet and go on to the symbol that pays twenty-five times the bet.
Each stop that moved pays 20 bets more than it paid before, every time the reel lands on it.
Over ten thousand spins the stops that moved bring back 700 bets more than they did.
Ten thousand spins are ten thousand bets staked, so 700 bets more is 7 points more: 85% becomes 92%.

Two machines can look identical and carry different figures. How a reel of ten thousand stops is mapped to the three or five you watch come round is a question this page leaves aside; what it does to an evening — the same share arriving in trickles or in one thunderclap — is the next one.

What the regulator puts in writing

The return figure in the regulator’s documents for Chile, and what kind of number it is
Document	What is in writing	Published by
The technical standard for slot machines	85% — the least any game may return, worked out over its whole cycle of play	Superintendencia de Casinos de Juego (SCJ)
The regulator’s questions and answers	the same 85%, explained: counted over a statistical series of about a hundred million bets, and not the chance of a prize	Superintendencia de Casinos de Juego (SCJ)

One national floor, explained by the body that sets it, and neither document gives a number about the machine in front of you.

What a machine owes the people at it is every combination that pays and the rules of its game, available at all times, even between games. That is a duty about what each prize pays and how the game goes. It does not ask for a return figure for the game being played.

Practice: which machine, and how long

Nothing spins here. Level 1 sets two machines side by side and lists what differs between them line by line, and you say whether any of those differences moves the share that comes back. The answers are not all the same: most of the differences move nothing at all, one of them is printed on the paytable where anyone can read it, and two of them lie on a reel nobody at the machine can see. Level 2 shows the counters after a finished run and asks what a run that long settles. Level 3 takes five things a return figure is read as promising.

Only level 1 is scored: every square on the strip below is one of its questions, and they are all there from the start. When they are full, level 2 begins by itself. Levels 2 and 3 have no squares and no score — there one answer fits every question of its kind, and a mark out of ten would be measuring patience.

The practice table needs JavaScript. Here is one question from it, with the answer.

Level 1 · Which machine

Same maker, two cabinets

Two machines, line by line

	Machine A	Machine B
Picture on the glass	the same game	the same game
Lands a prize on	8.8% of spins	8.8% of spins
Largest prize	on 1 in 5,000 spins	on 1 in 5,000 spins
Cabinet	this year	eight years old
Screen	bright	dim

Which of the two machines gives back a bigger share of everything staked?

The answer: Nothing in this list changes the share

Two machines can look identical and still give back different shares, and two machines that look nothing alike can give back the same share. A cabinet is not evidence either way.

Level 2 · How long it takes

Two machines: one gives back 85%, one gives back 92% · 50 spins each · one bet a spin

50 spins on each, side by side

Machine A

staked50 bets

came back35 bets

70%

Machine B

staked50 bets

came back40 bets

80%

After 50 spins each, how far can the higher of the two counters be trusted?

The answer: Not at all: right about half the time

Over 50 spins the machine that gives back 85% still finishes level with the machine that gives back 92% or ahead of it 49 times in a hundred, so picking by the counters gets it right 51% of the time.

Level 3 · What it will not do

A figure and an evening

At the machine

This machine gives back 92%, so nine evenings in ten I should come out somewhere near level.

How far does the claim follow?

The answer: The claim does not follow

An evening is not a short version of a machine’s working life. One evening is a single draw out of a very wide range of possible evenings, and that range only narrows after tens of thousands of spins.

Every counter in the practice table is a real draw from the outcome table of that machine, made when the page is built; the shares beside it come from the exact distribution rather than from more draws.

How the practice table works

Where the counters come from. Each counter on level 2 is a real draw from the outcome table of that machine, made when the page is built, so the picture and the figures can never disagree. Nothing is drawn again until it comes out a particular way: the question there is how long a run has to be, not who happens to be in front.

The shares beside them are not more draws. They are the exact distribution of that many spins, worked out by the same code as the tables above, because a hundred draws would land near the true figure rather than on it.

What is scored and what is not. Level 1 has a rule to learn and it is graded. Levels 2 and 3 are a reference you page through.

Where to look this up

Casinos in Chile Where these machines are, and how many of them each room lists.

18+ across Chile · Play responsibly · self-exclusion and the regulator are at the end of this page

Maya holding an open notebook, looking up from it.

Mayaformer floor supervisor · manners, money and breaks

Here is the practical half. The figure is not something you can look up for the machine you are at, and the counter on it is not something you can read. Which leaves two numbers in the room that are yours: how long you meant to stay, and how much you meant to spend. Decide both of those before you sit down, and do not let the last hour move either one.

If the money on the machine starts to feel like money you need, stop there and read the box below: it says where self-exclusion and the regulator are reached.

If it stops being fun

If gambling stops being fun, the SCJ self-exclusion applies in every casino in the country. Minimum entry age: 18 (age of majority under Law 19.221; Law 19.995 bars minors from gaming rooms). The casino may ask for an official ID. More on responsible gaming.

Show all regions

+56 2 2589 3000All regions · Superintendencia de Casinos de Juego — Central Telefónica

How it’s worked out

Sources, numbers and hosts

Where this happens. Every machine on this page is a cabinet standing in a room you can walk into.

Sources. Every figure attributed to the regulator is quoted where it is used, with the publisher, the document and the date it was read behind the button beside it. No publisher we could read gives a figure for any one machine on any one floor, and this page does not supply one either.

The two machines. They are ours, and they are not real games: each is a reel of ten thousand stops, every stop as likely as any other, and the two differ only in how many of those stops carry the symbol that pays twenty-five times the bet and how many carry the symbol that pays five times. No manufacturer we could read publishes a real reel strip, and inventing a real machine’s would be worse than teaching on a declared toy. The lower share, 85%, is the floor the national standard actually sets; the higher one, 92%, is ours, chosen so that the two differ by seven points on the same reel.

Numbers. Worked out when the page is built. What a machine gives back is the sum of its stops times their pays, over ten thousand; what a run of that machine shows is the exact distribution of that many spins, not a simulation of it. Every figure counts bets, never money: a flat bet of any size gives the same tables.

The model, stated plainly. Every table here assumes the same flat bet on every spin, exactly that many spins, and nobody stopping early. Real evenings do none of those things, so these are shares of runs of this model — not shares of people.

What is deliberately absent. There is no pace on this page: no spins a minute and no hours, so a run here is a number of spins and nothing else, and how long a run of that many spins takes at a real machine is left to the lessons that have a figure for it. There is no measure of how hard a run swings from spin to spin, and no figure for how often a machine pays beyond the one both machines share. And there are two teaching machines rather than three, because two is enough to show the point.

Hosts. Leo and Maya are illustrated characters. Their backstories, a former dealer and a former floor supervisor, are written for the course: neither is a real person, and neither speaks for any casino. The rules and numbers on this page come from the sources it cites, not from their experience.

No promise. Nothing on this page says that one machine is a better choice than another, or that a longer run is, or that an evening at a casino is. In every table on this page the machine keeps a share of everything staked, on both machines and at every length of run.

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