There are two types of players in this games: fast trainers (you get them for tokens from Youth Academy) and "flops", free YA players...

The highest SP gain of fast trainers = the lowest SP gain + 10, 20, 30 or 70 (Stretching, Cardio, Practice match or Official match)

The highest SP gain of "flops" = the lowest SP gain + 50% (for example, 6-9 / 12-18 / 18-27 / 42-63)...

These ranges go half down after age changes, 21 to 22, 25 to 26 and 29 to 30...

Sometimes, some players, once in a while, cross those ranges boundaries for unknown reason (and reason is NOT game rating, my DR just got 7 and SP 185 and his 99,9% game SP gain range is 112-182)...