Soft Target - S2-E6
Character mistake: On the roof, Don and the other agents have their weapons drawn on James Grace, who is holding Houseman hostage with the fake bomb. Once Grace is taken away, the threat is gone. But Don still has his gun pointed at Houseman, with his finger on the trigger. Houseman, while Don might think is a jerk, was innocent of any crime. There's no reason an agent like Don would have his gun pointed at him.
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.