When Jessica confronts the bellman he shows her the back of an upside down $20 bill. When the camera goes behind the bellman the $20 bill is right side up.
When Jessica inquires how & why her money on the roulette table doubled, Larry tells her that the chips were actually played on two numbers (13 &14) and that one of those "came in". He says that bet pays 2 to 1. Actually, that particular bet pays 17 to 1.