It is 28 Tank in one group, I think (I am not sure), but when a player attack you, the troops he receive from the alliance portal are separated from his own troop.
On this attack the player have 28 x S35 and 4 x plane MK4.
I check is setup, (alliance G.G.P , **** (his user name is 4 stars)), he is France nation.
He have right now 14 tanks, I think is a cheat to doubles the attacking troops or a bug.