Look at your sql query - see
Where RowNumber >= @RowStart and RowNumber <= @RowEnd
@RowStart
and
@RowEnd
are calculated from the parameters
pageSize
AND
pageNumber
So for the first page pageNumber should be set to 1 and you will return the first 7 records from your database. For the second page
pageNumber = 2
and you will retrieve records 8 to 14 inclusive.
The code is clearly working as it was intended to do - the SQL is returning the number of records that can be displayed on each page and as you work through the pages it returns the "next" set of records.