this guy is me LOL
mmmhhh ok amigo)) te respondo en inglés que sino me regañan
Ok, as marco say, the value is because the player of 4 millions train faster than the 2,5M player... that's the 1st thing.

the 2nd thing, is that, in some matches you will see if he works good, or if he have bad statistics. Usually, when a ST (delantero) scores 1 goal, in ...5 matches, this will be the tendence... and if he scores 3 goals in the 1st match like did my best player that I have now, simply this will be his usual level.
Puedes darme sus edades? a ver si encuentro la lista esa de fast trainers ...pero, cuanto mas joven y de mas valor, normalmente suben mas rápido, ganas seguro 1 skill point por entrenamiento del 30% maximo.