Mask arithmetics: Remove first, add second

[dosrobots]

Not sure if this is a common knowledge, but something l learnt today and decided to share it with you. When you're adding and removing mask elements, pay attention to the order: Remove elements first, add new second. Otherwise the outcome may not be as expected.

I assumed only the order of the layer mattered (add had that subtraction as a last item causing it not to work) Finally, after debugging the issue found the solution with Remove First -approach.

Illustration about the issue. In my case the 2nd option work as expected

[dosrobots]

UPDATE: Eventually I had to put part of the masking logic into subfolder (torso) in order it work as expected. Otherwise tableMask did not subtract elements from the outcome

Perhaps someone can explain how mask arithmetics should work?