I have observed something similar on some cases, that a player's game and training minutes are off by 1 minute. I am not sure, but I thought it to be some kind of a rounding effect of the minutes. I thought for the training the player has to fill the whole minute for it to count, so if a player needs 45 minutes for training, he has to play at least 45 minutes. In the game minutes we might see the mathematical rounding, so if a player plays anything between 44.5 and 45.4 minutes, it will be displayed as 45 minutes.
As I observed this in my cases, this approach always made sense, but perhaps it was only a coincidence. Maybe someone with more experience or one of the BBs can elaborate on that topic more.