API totalResultsAvailable diferent from web search

Hi all,

Can someone explain why All the API XML data for a web search where it reads:

"totalResultsAvailable"

Is different from the results of the websearch?, for example I use API to query the Keyword "Coffee"
and it throws 1,240,010,441 which is very different than
the result 1,270,010,886 from the manual search:

API search: http://api.search.yahoo.com/WebSearchServi...mp;query=Coffee

Web Search: http://search.yahoo.com/search;_ylt=A0oGdC...mp;fr=yfp-t-701

This is very frustrating, if data dont match then what's the use of the API? can someone explain?