@girish haha, yeah that's fair. Deleting backups is probably one of those tasks that should intentionally be difficult to do to avoid any issues (i.e. they need to delete the backups manually).
Only thing I can suggest maybe is a little icon designation either beside each of the backups that is past the retention policy (or part of a version upgrade backup) that explains it quickly and links to the docs or something, or maybe just one overall info button in the corner of the backups page or something. Not sure which is most feasible. I'll file a feature request formally for that though in a moment.
EDIT: I filed the feature request here: https://forum.cloudron.io/topic/4890/improve-the-backup-page-specifically-retention-related-items-to-explain-retention-policies-and-why-some-backups-exist-beyond-them