Im working on a small "for fun" project of a dps calculater. I just cant find any documentation on how the damage modifier is actually calculated.

Here is my best shot applied to an example:

Arbie with equipped with a t1 small em gun. Ingame mod = 191%
Em gun 135%

Skills
Racial skill (5) = 5*3%
Bot skill (5) = 5*5%
Target Analysis(1) = 1*1%
Total 41%

Then apply the 41 to the 135 :
(135 * 0.41) + 135 = 190.35%

Could it just be a type conversion rounding somewhere, or is this actually way off?
Notice 135 + 41 is nowhere near target.