Delay purge doesn't seem to be working If you want to keep backups for 90 days, then I would set Delete Versions Older than 90 Days. I think that would do it. Now you'll end up with 120 Days of backups before the oldest backup set can be removed - returning what's in backup storage to 90 days. I think you can leave the Number of Versions option unchecked, but I am checking with the team to make sure I've got it right. I'll reply back tomorrow with confirmation.
In the meantime, you'll need to set something if you stop using the default options - your screenshot doesn't show any retention options set when overriding. Or return to the default options until tomorrow.