The "way things are" for Windchill: - Delete applies to latest - Purge applies to non-latest with ability to use some filters May be able to create a simple purge job for this one object - BUT there is no filter for NUMBER so will be challenging. Could move the object to a different context / folder and then use this filter for purge. It's actually a very good thing that it's difficult to remove non-latest - and non-admin users absolutely cannot.
Welcome to Windchill. No selective delete. No purge selective revisions. No delete everything but the latest X versions. You have two options. You can delete everything from the latest backwards using the "Delete" function or you can use Purge from the first iteration forward (but never get rid of the last iteration of each revision).
As long as A.1 is the first revision in REV A (no A.0), you should be able to use purge for this. I'd recommend temporarily moving object to a separate, empty product (or library) while doing this. It makes things much simpler.