Why is it happening?

Today i just tried to search YAHOO!! (Plz don't laugh) on google just to find how many links to yahoo is available.

after entering zimblY "Yahoo" in search field and pressing Search buton i got

ie: 542,000,000 Results for Yahoo

then i started looking every 10th page

when i clicked to 37th page (as link is given)

it opens 36th page instead of 37th

showing result of 351-352 of 352 results for Yahoo (????)

and a note in the last

"in order to show you the most relevant results, we have omitted some entries very similar to the 352 already displayed.If you like, repeat the search with the omitted results included."

(ok this thing is acceptable)

then i tried it again with included results.
and this time i got


ie: 646,000,000 results for yahoo in 0.06 seconds with all results included , and supposed to be shown.

but
this time again
when i reached to 92nd page

it shows


911-913 result
this time without any note


nd that's the end.





so where are rest (646,000,000 - 913) Results.
it does not happen in this case only
if you search for relatively rare term also it may result into only 6 - 7 result even when its showing 25 results found.

i understand all those result are generally not relevant.

but can any one describe whats the criterion of google behind showing
this much number of results.

is it the number of links available on
web pages instead of number of
results???