system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How a casino knows that you're counting cards in your head?

So Ben Affleck has admitted to counting cards and was told not to play Blackjack at certain casinos. How does a casino know that he's counting cards if all the math is done in his head and they can't really prove it.

Thanks for the explanation and tips. Much appreciated.
gpt
They don't have to prove it. They watch your play style and if you are playing very well for a long time and appear to be matching the results of a card counter, then buh bye. It's not a right to be in a casino.