Substance Painter - Masking bug selects whole mesh

Anth

So not too sure if i'm just doing something wrong or its a bug, but whenever I select which generator I want to apply to my mask on my fill layer, it changes the mask so it has selected everything and the generates the whole mesh; instead of just the small section I masked. 

If this isn't a bug how can I just add a generator to the previously masked parts instead of everything?

Froyok

You need to change the blending mode of the Generator filter. By default it's "normal", which means it will cover any areas. Try to set to multiply or linear dodge instead (depending of what you want to achieve).