I always wondered why I wore one number under my warmup while sitting on the bench for home games and a different number under my warmup while sitting on the bench for away games. Also, I used to sneak candy onto the bench because I sat on the bench for home and away games.In the NCAA players can only have digits 0-5 in their numbers so that refs can signal their fouls with two hands, one hand for the first digit and the other hand for the second digit (if needed).
Apparently years ago in Iowa high school basketball schools had one set of jerseys (home, I think) that had all even numbers and then the other set that were all odd for the road. A player might wear 1 at home and 2 on the road. That way officials could signal a foul with absolutely no confusion as to who it was on since there was a unique number on every player that played in the game.