Continuity mistake: When Charlie explains that his map was generated by an equation he writes the equation in abbreviated form on the whiteboard, and also when he writes the equation for the probability of winning the lottery, in following shots the handwriting changes and some of it vanishes and reappears.
Continuity mistake: While Don's at the parking garage with Rachel Abbott's car he realises that the killer had been watching Karen Silber's house, and when they rush off to her house there are white security bars on the windows and front door in the long shot and also later in the news footage, but when they're at her house none of those bars exist and the shrubbery also differs.
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.