This is actually the college rule -- that neither digit can be higher than five, so that the referee can signal a player who has committed a foul with two hands in one motion. In fact, up until... 2000, I think, a player couldn't even wear 1 or 2 because those numbers were used to signal foul shots, and thus would be confusing. Obviously, they didn't think it'd be confusing enough, so they removed it. If you think about it, FIBA's system makes sense because, like college, the 4-to-15 system makes it easy for referees to signal a foul in one motion, as all of the numbers can be made with two hands. This is the sort of stuff you take for granted as a fan until you scorekeep a youth basketball tournament and the referee has to go into odd contortions to call a foul against #38 (and you have to figure out just what the :censored: he's signalling). hahaha. well i wasn't too far off, thanks for clearing that up.