How do the update numbers work?

Ok for our most recent update, I would like to explain that the first 2 in 2.1.0 is a signify if a major. update such as new mc update or spawn or something like plugins added/mods added, the 1 stands for a medium update such as new staff member or extra spawn stuff/etc., and the 0 at the end is for small updates within such as minor tweeks on the server's running/world