The number 2 because you have a tie game working for you, which means a team has a chance for a last second bucket to win the game by 2..........similar to a winning FG in football, but not nearly to that degree.
The number 7 becasue in a close game, teams will foul late, and for whatever reasons, the number 7 just happens to fall more often than other numbers other than the number 2(but they are very close). Some will argue the number 5 is just as "live" as the number "7".......but I disagree.
If your not paying more then 7 cents for a half point around the numbers 2, 5, and 7, you have a longterm win.