Google Tweaks Its Number to 3.3 Billion and Adds "Supplemental Results"

Well, it looks like it took AlltheWeb announcing a larger size than Google to get Google to finally update its claim to 3.3 billion. Since And I don't know if this is related or not, but I have suddenly found a few hits that Google labels as "Supplemental Result" right before the cached link as in the last record on this search. I'm not sure what this "Supplemental Result" is supposed to be, but the URL is a dead link. I certainly hope Google did not just boost its numbers by adding a bunch of dead links. I rather doubt this is the case, and another such search found a record with the same label, but that one is not a dead link.

Wait . . . a little more searching turns up an answer on Google's How to Interpret your Search Results help page where it says that

"Google augments results for difficult queries by searching a supplemental collection of more web pages. Results from this index are marked in green as "Supplemental."

I am assuming that this is new, in part because doing a site search at Google for "supplemental" results in zero hits, even though they have a help page with that answer. But I'd like to see more description somewhere of what this supplemental collection consists of.