In total 4 players didn't train today.
Their stamina level didn't rise
Ok, understood. In that case, maybe it would be wise to rephrase the text about stamina-free throws and game shape in the rules.
The first training area on the list is Team Training, and this works a little different from the rest. When this is selected, the second menu lists three choices for training areas: Game Shape, Free Throws, and Stamina. For these attributes, it is easy for the coach to train all of the players on your team (he can have them shoot free throws for an hour or run laps around the building), and they dont depend too much on in-game practice. Therefore, selecting one of these options will train your entire roster, whether or not they play in any games that week.