I understand that after we get the Supplemental Update we gonna have the option to buy upgrades for our weapons.

My question is for those how know how it works. How does upgrading the % on weapons work? For example, if I have a 38% Rucar can I up grade it to 50%? Or is there a certain limit? For example, is the limit something like not over 40% or something like that? Or is the limit like you can only add 20% to that said weapon regardless of it's current %?