So, I was in vanilla6. 15 mice and I got 2 firsts, I was supposed to have my 600 firsts, but it didn't even count. I'm mad right now.

Is your cheese not counting either?

As you said there were 15 mice, there could've been the possibility of some people being on alts. Firsts only count with 11 Unique IP's

This happened to me in a room of 16 people a few weeks ago. Turns out they were all using computers in the same room in school. If there were 15 mice and your firsts didn't count, it was probably because at least 5 of those players had the same ip address, or were in the same range.