Use Urls from global lists if exist
This means that every successful submission/verification/identification... is logged to a file (global options->advanced). URLs from that file are shared between projects and can be used here.
Use Urls linking on same verified URL (supported by some engine only)
This will go to a site that holds more than your verified URL (usually blog comments or similar engines). All external URLs from that page are used as possible target URLs in the hope that some people use it as tier target.