i think your already has 10%...that is the max you can get... and in the normal training ... 8% to 10 % is....really hard.... i try...spend like 100% green to do that... for by training all my 24 players..... and 2X mean if the attack bonus process 20% or point at the picture above in your training, you will gain 40...so that you can get faster to get the next 2% bonus~ but in 10%.... nothing will be add because that is the max~ so..i think that is not really useful...only to eat you 20 tokens~