No i cannot do the calculation. I'm not that clever rofl.
however even i see that this is incorrect. Take this for an instance you are using 2 buffs to achieve 1800% and one spell has 900% each. in theory by + this would work!
BUT you are additionally INCREASING 900% BY ANOTHER 900%
this is how it looks atm " 900% increased by 900% " and this is based off your base damage so 900% of 108 equals to 972, but now if you do 900% of 972 that would equal to 8748
and you are not doing 900% + 900% this is 900% increased BY ANOTHER 900% of that earlier base stat and 900% from the beginning, so that is where i think it fails.
BUT it could also be that the core just don't allow it *yet* to be able to have 1800% cuz it'll break the game.