A lot of these disagree with my assessment, and it's not clear why. Should I click every square which has some pixels of the object? Apparently not? Apparently

A lot of these disagree with my assessment, and it's not clear why. Should I click every square which has some pixels of the object? Apparently not? Apparently I'm supposed to click the squares which contain only the bulk of the object. Sometime it seems if the object in question is also in the background, I'm not meant to click that one? And sometimes I am. I hate these these things.