Do you mean if you're not training that position?
You only get training for minutes played at the position that you specify.
So if you're training PG/SG for the week, only players who play at the PG and/or SG position for the week will get training.
For example:
Training PG/SG
Player A - 48 minutes PG
Player B - 20 minutes SG, 28 minutes PG
Player C - 48 minutes SF
Player D - 48 minutes C
Players A and B would get full training for the week, players C and D would get none.