If you can see the atk increase in your status window then it works like if it was part of your normal atk status aka doesn't work like a mastery but like it was a zipper bear card.
Another way to check how stuff works is just look at the script at rms and compare with the one in the zipper bear card, for example.
zipper - bonus bBaseAtk,30
naga armor - autobonus "{ bonus bBaseAtk,20; }
tae swrd - autobonus "{ bonus bBaseAtk,50; }
Bolded stuff are the same, works as the same, calculated before the multipliers being applied.