Version vs release naming schemes

What's the relation between the Month+Year release naming scheme (e.g. Jul2015, Oct2014-SP2) and the numeric versions (e.g. 11.19.9)? The website has a release history page: https://www.monetdb.org/Documentation/UserGuide/ReleaseNotes But I haven't found a page discussing the numeric version numbers. I'm not even sure the X.Y.Z format means version.subversion.subsubversion ... Eyal