Uh, this is really up to you, lol. Generally, though, you should follow SemVer, IMO. SemVer mandates that the version is divided into three parts (MAJOR.MINOR.PATCH) where the patch level is incremented for bugfixes, minor level is incremented (with patch level reset to 0) when there is a non-breaking API change and major level is incremented when there is a breaking API change.