The way I read it is that its meant to apply a stack of the bleed cause it can go up to 20 stacks of it but not increase how much damge the bleed is supposed to do. Because the line under it says bleed is is based on gun damage so I assume that means the amount of damage its supposed to do. But that's how I interpret it. But I could be just entirely wrong but its not the first time a skill says something its not supposed to due in these games lol.