At this step of the Automatic Submission Wizard, you can tune-up your selected download sites and categories where your product is going to be submitted.
You don't have to manually pick sites where the most recent version of your product was not yet submitted. RoboSoft will never submit the same version of your product to the same site and it will wait for two weeks before submitting a new version of your product to the same site. It is perfectly safe to select all the download sites at this step. The risk of being banned for spamming download sites is quite unlikely with RoboSoft.