What game was he playing?
Sylvester was supposed to be playing baccarat, but that was not baccarat. Seven is not a natural - only eight and nine are naturals. He didn't have to announce that he was going to stay with the seven. You don't have choice. Seven does not hit. Bacc rules. He also didn't have to tell the other player to hit his five. Again, bacc rules don't give you a choice in that situation. And shouting 'that's a bust!' is also wrong. There is no busting in baccarat. The writers seem to think bacc and blackjack are the same game.
I understand bacc was supposed to be foreign to Sly, but the second he said anything about betting player because 'that's me', everyone would have known something was up.
Someone on another thread said it seemed like the writers weren't trying very hard on this episode, and I have to agree. (But just because I'm commenting on the errors does not mean I dislike the show at all. I just think they're capable of better - and their viewers deserve it.)