I think these numbers relate to the build version number, e.g. my Nokia 8 has build version 00WW_4_84A_SP02. Unfortunately I don't know what the build version on previous Android versions was.
So whilst HMD are releasing some of the kernel source code, they're still far from perfect. Several phones have still not had a release, even though they were released a while ago, e.g. Nokia 5, Nokia 2.
Also, not all software versions for each phone have been released, as far as I can work out. The security patches page gives a clear list of the different versions of software for each phone: https://www.nokia.com/en_int/phones/security-updates