The figure displayed increases in a non linear way, it's just a representation to compare to other weapons. Your actual accuracy will have increased by 16%
Aurel once confirmed that accuracy numbers are used to compare / represent weapons within each category to each other, so I'd assume yes, otherwise that wouldn't be a very good representation?
The numbers physically change when u add the mod. So if they are not an actual representation of the weap accuracy then what is the point of having it there to see. Very odd and missleading.
As Harley said, to give a comparison. I agree it's a stupid formula. The change is a reflection of the mod bonus, but it's weird and convoluted for no reason.