You can have several players play in one position, but you want them to get to the 48 minute mark. Since there are 3 games to get training, to max it out you will need to play 3 different players for an entire game at the selected position to get the most out of your training.
so if you are training PG for example.
Game 1 (Sat) - player 1 plays whole game at PG for 48 mins
Game 2 (Tue) - player 2 plays whole game at PG for 48 mins
Game 3 (Thu) - player 3 plays whole game at PG for 48 mins
all three will get full training at PG position.