It is a numbering scheme used by most "shops" around the country. It sets the matchups of games in a particular order such that everyone in the industry can easily refer to the same game by its number. Line Updates and Weather Reports are given in the order such as "Game 52 gone to 8.5 circled, bad weather" Translates to: Regarding teams 51 and 52 on the Nevada Rotation, the favorite's line has changed to 8.5 and there is now limited action due to bad weather." Perhaps the most common use is by the Casinos, when the "phone accounts" call in (those people who have set up accounts by depositing money with the Casino) the odds can be updated without speaking the team names, such as " Here's the latest line, 2, 3, 4.5, 7, 19, 2, pick-em," etc. This means that teams 1 and 2, the line is 2, teams 3 and 4, the line is 3 etc.