I have a website, which is showing "About 222,000 results (0.39 seconds)" for "site:domain-name.com". When I go to the last page (14th page) of these results, it changes to something like this: "Page 14 of 138 results (0.20 seconds)". So in the end, it looks like the number of available pages is 138. Can you tell me how does it work, and what it means. Are these pages in the supplemental index, and not really accessible through Google.com? How does it work? Thanks. I heard this is a number of pages cached by Google.com I am showing a number of 320,000 in Google Webmaster Tools, and also some online tools. How does it work?
Tell us your website please ! About that changing thing, keep in mind that google removes results that might be considered duplicates when advancing into search results
As @King Manu mentioned - Google is probably seeing some of these as duplicates. Does each page have unique title/meta tags?