It doesn't really matter, any more than the blueness of the eyes matters. It's just that there is still not enough information to solve the puzzle even after knowing the sum...

Full answer is posted in I and A, "Answers to puzzles", located here: http://wordsmith.org/board/showflat.pl?Cat=&Board=announcements&Number=131223
at the bottom (today, anyway).

But it's not whited-out or anything, so only look if you really want to know.