Second notification on old Unread Mail

I think this is an old subject but since I’m an old dog, I still need help. The issue I’m having is that unwanted notifications occur when the following happens:

For example, I have set K9 inbox to download 50 Emails. When one (or more) of these 50 Emails is deleted, K9 will replace it with an older Email. (Previously Email #51) If this email happens to be unread, I get a new mail notification.

Is there a setting that only notifies when the mail is new?