What does 1.0, 0.1, 1.1 and so on mean?

[egosnell2002]

Hi, I was wondering about the numbers that are put in front of the species of snakes people own, that is normally at the bottom of one of their posts, for example:

2.1 pieds

0.1 albino

and so on. What do these mean? Thanks for your help, Ethan.