This is one of those "urban legend" things that seems to come up every so often. I heard it last year about the numbers for the year before, etc.
Google has changed the way they store pages and return results. They have marked many pages as "supplimental results", which some people suggest comes from a seperate but parallel list system. These are older pages, retred pages, duplicate pages, and pages that have redirected over time.
The "google number" is only a number. Trust me, they don't go out and recount the number of items in their database for each visitor. They may have stopped updating it, or there may be a limit only on the size of that field. Either way, I make new sites, they get in there, and the old ones are still there too.
Thank you to whoever deleted all those pages so I would have space.
Alex