let see the screenshot in the opening post... base attack is 1782, attack against archer is 245% incrzase, attack against other type of troop is around 195% increase... difference between 195% et 245% is 50%, who is the normal bonus for calvary against archer...
so, seem that formula is somehow like BasicAttack * ( 100% + Unknow95%AgainstAllTroops + 50%BonusCalvalryAgainstArcher )
against archer : 1782 * ( 1 + 0.95 + 0.5 ) = 1782 * 2.45 = 4365
other troop : 1782 * ( 1 + 0.95 ) = 1782 * 1.95 = 3474
seem that calculation fit almost the number in the screenshot from the opening post... bonus of 50% from calvary against archer is apply correctly...
but now, need to find what is these 95% bonus attack who is apply to all troop...
by example, in my case, invader research tree, troop attack II at 12/15 give already 28%... a scrool 10 min troop offense 50% increase it at 78%... VIP lvl 25 give 23% extra...total 97%
already over the 95%... trick is to find what bonus apply on the basic data ( 1782 ) and what bonus apply on all type of unit offense ( the 95% in this case )
same if it remain some unknow, it have be proven that the 50% bonus of calvary against archer was apply correctly... topic solved