What is the reason for v00 in a G000V00 GDG?

This is the version number and we can have upto 99 versions for the same generation.

Say I have 5 generations of a file, but I have to make a change in gen 3, I will have to create a new version and copy the data in gen 3 to it. but before I do this, I will have to take a backup of the data in G003v00 as creation of G003V01 will erase G003V00.