Deleting in Gmail

I was cleaning up my gmail just now. I started by deleting lj comments, because they're the messages I'm least likely to go back and look at (and besides, they're saved here.) So I got to the point where the header said, "20 out of about 200." And then I started counting, because I was pretty sure there were a lot more than 200 lj comments still in my inbox.

I got to eighty-nine deletions of twenty emails each before I was down to zero. That is, it said I had two hundred - and I actually had closer to two thousand.

You'd think a computer program would be a little better at estimating than that. For that matter, why would it need to estimate at all? I don't get it.