All's Fair - S2-E18
Revealing mistake: In the scene where Don and the FBI crew is investigating the body of the Iranian victim, a split second closeup on the head of the Iranian woman shows she is breathing even though she's been dead for an hour already. (00:04:00)
Answer: Craps is a casino game where players bet on the outcome of a dice roll. It deals heavily with probabilities and is a favorite of math experts like Charlie. Whatever the odds, though, your chances of winning are much greater than winning the lottery.
If you bet against the roller in craps, your odds of winning are about 49%, which is as good as you get in Vegas. The point he's making (though it's pretty obscure) is that if you're going to bet, you may as well bet on something where you have a slim chance of winning, as opposed to the lottery, where your chances are basically 0.