Ayush,
If thats the case then your scorecard is working as per its standard working.
If you map 21 rows to a scorecard and it can show only 15 rows at a time then it will show the scroll bar for sure, it doesn't depends dynamically on the number of rows. And in your case its working like that only.
So you will get the scroll bar in that case.
If you select the Ignore blank rows than it will show lines till data and will increase as per the data coming.
Regards,
Javed