Yeah, I was using it as a sigma, and misusing the hell out of N (using it as both the variable and the max of the sigma range). Figured it would make more intuitive sense that way to people who wouldn't recognize a sigma, but apparently I just made a mess of things.
Ok, I'll do this with rigorous notation instead of the "trying to fit this into one line" that I did before.
2. Sum for n = (1..N) of the values ( Max(1,a-d-n) )
Note that N has a max of 5 for bosses.
Make sense now?