emails in recover delete items list

Okay so on Outlook 2016 under Folder tab there is a Recover Deleted items icon.   I have a few users now that have items going into there on a random basis.  The items that seem to go in that list have no rhyme or reason.  Some are items that have been moved to another folder (and still in the folder) some are task items or contact items that show in there (also still listed in the task or contact sections) and some are new emails that never seemed to make it to the inbox.  Upon contacting Microsoft they said it has to be a rule.   The problem is there is not enough consistency to be a rule.   It will be only one from a sender while others are coming through fine, it may be some with a specific subject but not all of them, some are items moved between folders but not all of the items moved as part of the group.  Also, one of the users that are having the issue (really noticed because of some emails never making it into the inbox) does not have any rules in place.  

So my questions are:
1) what are the determining factors for items to be moved into there?
2) where does it return the emails/items to when you restore them?
3) is there a way to edit the settings that govern that feature?