That's odd, Mr. Miserable Driver . Who knows the mysterious inner workings of this place? By the way, mine says "1093 posts (440 new)" (I haven't read Weekly Themes since June).*
If'n I had to guess, though, I'd say the originating post would be the "extra" one that's being counted.

*Yes, I know I said I'd read everything eventually. Eventually's just going to take a little longer for that section.