The description of finestra is applies an additional critical rate to your spear attack, here’s the situation:
my critical rate is 4000, enemy’s critical resistance is 3000, and the formula is Crit chance % = (your critical rate / enemy’s critical resistance)^0.6 -1
so, my critical chance without finestra is (4000/3000)^0.6-1=0.1884
now with finestra, which offers 48% additional critical rate, what will my critical chance be:
will it be (4000*1.48/3000)^0.6-1=0.5036
or 0.1884*1.48=0.2788?