GoogleGuy - 6:16 am on Aug 27, 2003 (gmt 0)

Hey, the supplemental results are a new experimental feature to augment the results for obscure queries. This is a new technology that can return more results for queries that for example have a small number of results. So it might not affect the results for a popular search, but for a researcher doing a more specific query, it can improve the recall of the results. The supplemental collection of pages has been collected from the web just like the 3.3 billion pages in Google's main index.

Hope that helps,
GoogleGuy