Running a scan: check a domain against the index
The scan checks a domain against the index we have already built. It is a lookup, not a crawl: no request touches your site, and the answer arrives in seconds because the measuring already happened in the background.
What a scan returns
Four counts are free and need no account: how many of the directories we have crawled list the domain, how many of its links are live, how many sit on pages Google has never indexed, and how many links it has lost. One named finding is printed with them. The per-listing breakdown, which names each directory, links to the page we read and shows the link's rel attribute, is sent in exchange for an email address. That exchange is stated on the page rather than discovered afterwards.
What the scan cannot see
The scan answers from tracked directories only. A listing on a directory we do not track is invisible to it, and a directory that blocks our crawler contributes only the fact of the block. The directories index states the corpus the scan reads.