To find out what a casino pays out, you’d need to add together the RTPs of all the games offered and work out the average payout across the casino floor (whether virtual or real). In practice, it is much easier to decide on the game you want to play and to find a version of that game offering the best RTP for you.
Different gambling commissions will demand a minimum payout percentage for each game. However, in practice, most games and casinos will offer a far higher payout percentage for each game. Slots are a good example of how the payout percentages can vary. Some are around 95%, but a game offering a payout of 98% means $98 will be paid in prizes for every $100 wagered. That means the casino would keep two dollars out of every hundred.
However, you should remember that is calculated over the total number of plays on the game over time. It doesn’t necessarily mean you will get back $98 for every $100 you play. You might win less than that if you go on a bad streak. On the other hand, you could win a huge progressive jackpot on your second spin. No one knows how an individual will experience a game, which is why you should always work out what you want to bet on the game before you begin.