Custom paging issue

I think it is working as expected. Because this new row count should be applied from the current page. So from the User Experience standpoint, this looks right to me. Because let's say you had rows till 3700, then when you start from 3631, it will show you all the rows till 3700 but because you don't have more rows to display, it is not showing any. So this looks correct to me. 

You can also set the startIndex back to 1 if someone changes the value in the dropdown. 

but when I am choosing 100 has drop down than I have 32 as total records in last page . So should I not accept that my start index should move from 3631 to 3600 ? this can be possible or not I have also doubt but I tried putting some calculation but it is not working.

It is possible. But to me, it won't be a good UX. Still, if you want to do it, just mod the total count by 100 (or the value selected in the dropdown) and set the output as the start index. If the output is 0 then divide it by 100 and set the output as startIndex. 

I tried like this but didn't work can you check this  is it the same logic as above or I missed something

if(
mod(ri!totalCount, ri!pagingInfo.batchSize) = 0,
ri!totalCount - (ri!pagingInfo.batchSize) + 1,
(
floor(ri!totalCount / ri!pagingInfo.batchSize) * ri!pagingInfo.batchSize
) + 1
),

See that is the problem. You need to show 100 records from where the person is already, which is the start index. So if you move back the start index, they will start seeing the records they have already seen. Getting it?

But according to my current use case they are fine with it as a user

But according to my current use case they are fine with it as a user