Document version offset numbers

[felixcremer]

According to https://docs.binarybuilder.org/stable/building/#Version-number the version number of the jll should match the version of the source. This is not always the case because sometimes the version number is multiplied by 100 and some version offset is applied.
It would be good if this could be documented.

Some context:

I am trying to understand how I could recompute the version number of the source from the version number of the jll in a generic way. Is there some indicator from the JLL whether or not this version offset was applied?

My initial use case is to fix the same version from the JLL as I would get from Conda so that the python and Julia packages would play nicely from the same process