Today, it's a best-practice to use SemVer for versioning. It defines that a version is made up of three parts: major, minor and patch, for example v1.0.0, what each part represents and how version bumping works.
While for end-users, dropping the patch version is a thing (e.g. v1.0 instead of v1.0.83; who cares about bugfixes anyway? Users want features!), I have never seen a version start with a period. Maybe you found a typo?