That's what I get for learning programming years before entering college. I forget standard mathematical notation, since I always use programming language operators (like ^) in my head. Further, I only checked the first row to make sure it was actual addition, and obviously 0xa0 + 0x04 == 0xa0 ^ 0x04.
I should've just checked here first (includes an image of the slide in question): http://stackoverflow.com/questions/839479/what-does-a-circle...