I don't know why there might be a difference on different clients. But reporting that 13-6 is the current when the latest would have been 14-6 (in your post), could be that there is an out of sync between what is reported and what is actually displayed.
On the stand alone versions a repair of avast has been know to resolve the out of sync condition (I don't know if this would be the same on a client system, if a repair can be done or not). If there is an out of sync condition, I just wonder if that might have a knock on effect on the avast housekeeping of old defs, VPS sub-folders.