for example air brush painting is not fully opague ? in Affinity Photo

[MxHeppa]

for example painting is not fully opague ?  looks like this:
i painted this black and when i pick color is 63,63,63. and in border areas there is darker values than middle. this happens other brushes as well. and used red does same. i feel this bug. i want for example airbrush stuff what is rounded edges but darkest area is black when i select black. in other program i can do what i want (and i feel there should be also happen same)   but is so silly use program what is very old (is i think 1993 or 1996 or something like it) and change stuff to it and back and even more worse this other tool dont support modern wacom and multiply mixing mode for example,

[MxHeppa]

in pixel mode i can do what i mean but loss smooth edge etc. i imagined even normal paint brush tool mode darkest area should be black (or what color i selected) with these brushes but here is not.

[MxHeppa]

i found one brush style looks do what i mean. is hard found this. becouse of this i have feature suqquestion what i going post.

[PaulEC]

It looks like you have "Wet edges" selected!