Understanding when backups are deleted

To answer your specific example, you should check the setting in Advanced: "Automatically remove backups older than...".  I think this is off by default so BB will never remove backups.

You can either turn this on, or run manual cleanups when you feel like it.

Generally speaking, when you run the cleanup BB will remove backups of a file after 30 days from the moment it first sees the file doesn't exist any more (doesn't matter if it's been sent to recycle bin, fully deleted or even just moved out of BB's world view - just being absent is the key thing).

However, if the file has several versions it may not be able to delete earlier versions even if they're older than the 30 days, if there are newer versions. This is because the versions are "chained": each subsequent version is a delta/diff of the previous version.

For example, if there were two versions of the file, 31 days old and 29 days old, neither could be deleted because the latest one is still "alive" (and depends on the previous one).

Wait another day, however (so they're 32 days and 30 days old), then they can both be safely deleted.

Hope this helps.

John