CurrentVer is the version number served as current. It always equals versions: numbering is dense from 1, and deleting a prompt takes its whole history with it rather than leaving a gap.
Versions is how many revisions the prompt has, COUNTED in the store and uncapped — so it can exceed the 100 entries a list row or a detail response carries. Note the type: here versions is a number, while on a list row it is the list of version numbers.