How to stop Autoblog from adding back deleted posts?

I purchased Autoblog a few days ago and have it successfully working on one of my sites. However I've noticed that it keeps "adding back" posts that I've deleted (I delete some posts that I don't think will be of interest to our audience).

How do I stop Autoblog from "reprocessing" posts that it's already added and I've deleted?

Thanks, Chris