In your demo, and on my usage I noticed the pager numbers were not correct.
http://demo.koolphp.net/Examples/KoolGrid/Paging/PrevNextPager/index.php
If there are 10 items on a page in the pager, then it should be :
Page 1 : 1 to 10
Page 2 : 11 to 20 etc...
But the pager is saying 1 to 11, 11 to 21, etc...
I think the pager has a minor logic bug. Could your dev team check this out?