One title is not one game
Imagine the same film being shown in cinemas on two independent circuits. One circuit runs the movie as it originally appeared in the cinema, the other as it was eventually put out for television. The same movie, but two different things in the two copies, not just in the framing or ads with it, but right down to the pictures and sounds. The title is the same, but the event is different.
The same is true of a slot title. It can be supplied in more than one configuration, each with its own conditions and pay-out percentages. Blackjack, roulette and poker titles often ship that way, but slots, too, are likely to arrive with several forms available: the choice of which one the player ends up playing is a question of the copy that the operator subscribes to from the game studio and not a choice the player can make.
That is why the figure you find from comparison site round-ups and review site paytables is not a guarantee, even about what the title itself is saying on its own information, help or paytable screen. The figure on that page accurately describes a before-title game which is posed to sell the title to you and to describe it, but does not point to the copy that actually opens when you tap on the title icon in the app. That does point to the figure you need, and it is an accurate figure, because it is not on the website but on the title itself.
Where the figure for your copy lives
One click is all it takes to get there: from inside the title, not from the lobby or review page, and not from the operator's Play Now button. The figures lead the player in and back out, but do not state what they are describing.
The figure for the copy the player is playing is stated in the game’s own information, help or paytable screen, reached from inside the game and not from the lobby tile or a review page. That saying does not mean that the figure cannot be hidden in those places, too: but the information, help and paytable screens are the only way to be sure.
On a phone with the game open, the information route can be a menu button (the one that looks like Apple's multi-tasker over there on the far left) or an information button (a one clearly marked in English on the right), depending on the title. Look for where you could seek technical help on the game. On some titles that takes you to a pop-up screen with no links on it, on others to a static screen whose only actions are links to open the app’s bottom bar, or to leave the game. Look for a section on understanding the game or on returns.
That section will not always be called 'Return to player' or even 'expected percentage return'. Where a game expresses everything in terms of win rates, getting from a 95 per cent win rate to a 95 per cent return involves plugging two plus numbers together in lieu of one of the original return to player numbers: do that and you get the manufacturer's best estimate of the return to player percentage. In those cases, the fewer the plus things are, the closer to the return to player percentage you will be.
The figure will normally read as 'The game has A return to player percentage of N per cent, where 'N' is a number from 90 to 99, sometimes a decimal figure. The figure is expressed as an average share of stakes returned over many rounds and not per initial credit. The table may also state where the figure comes from and what it includes.
What the number means
The figure found in the game's own guide section is a long-run average, not a promise about your play or anyone's. Even though the word 'Player' is used in everyone's return to player.
Return to player is a long-run average share of total stakes returned across very many rounds. It describes the game, not a session, and it is not a schedule of payments. A 97 per cent figure means the game returns, in aggregate, 97 cents of every dollar staked, but that is not divided by spin: on a favourite of yours, the game may well pay out far less, or far more, in any similarly long run. So it is a useful measure if you are a high-volume player, stay at it long enough, and do not hit a single spin hazard: until then, turn would not always land where it ought. But it is a title-wide statistic, is not itself a promise, and there is no hard promise behind it.
Where the payout table matches the return to player percentage as both are given in both sections, then the table accounts for everything dismissed or discarded from return to player, such as rounding or average multiples. Where they differ, return to player looks more likely to be complete, but that is not a guarantee.
Why two sites disagree and both are right
A single stated figure can also cover a game whose return changes with a chosen bet option or side bet. Where that is so, the information screen is what states which option the figure describes. So two operators can publish different figures for the same title without either being wrong, because they are describing different configurations. Just as two translations of the same film can be accurate but expressive of different vision.
To the player, there is no alternative to looking at the figures on your phone to discover how your time has gone. All review websites cover is Play Now links to get a player to casinos. What percentage you earn, how you seem to do, that depends on which title you chose and who is currently running it.