[TYPO3] Indexed Search results problem

[Hraklis Karvasonis]

Hi.
I am using indexed search 2.1.3 on TYPO3 3.8.1
When i am searching a word on my website the search result page shows 
that there are 7 pages with 65 search results.
But if i click on page 7,  a blank page with no results is displayed and 
it says that the results are 57.

Has anybody seen this before?
It seems that the extension calculates the results on every page 
separately and in the last page it has fewer results.

Why doesn't the extension count the total number of the results 
globally, so that it will be the same on all pages?

Does anybody have a solution for that?

Thanks.