Lol, that's probably one of the most common questions. I had a few people PM me asking about it.
Ok, the numbers represent how many animals of that type're in a collection, and what sex they are.
Example: 2.4.1
BCI <--- This would mean they have two males, four females and one un-sexed constrictor.
It's just an easier way of telling everyone what you have.

Don't worry, it confused the crap out of me at first as well.
Like my own sig, too.. three male ball pythons, two females.. one male columbian, one un-sexed.. etc.

Once you know what it means it makes a whole lotta sense, eh?