This is just my theory on training, but I've been thinking the percentage of 48 minutes is squared and this is how much of the training is received for a player who hasn't reached 48 minutes. For example:
36/48 = 75%
75%*75% = 56.25%
Therefor a player with 36 minute would get 56.25%
This is just a theory, but it seems to have worked so far for players of mine who have gotten partial training. I have used it to make tough decisions when my minutes have been messed up. Anyone have thoughts on this?