This might be because of the join condition you used.
s.no=e.no
This might be true for more than one row leading to duplication and hence wrong result.
Example:
Table A
No Name Qty
1 ABC 10
2 XYZ 20
3 QWE 30
Table B
No Name Qty
2 XYZ 40
5 DFG 30
2 XYZ 40
Table A Left Join Table B:
A.No A.Name A.Qty B.Qty
1 ABC 10 NULL
2 XYZ 20 40
2 XYZ 20 40
3 QWE 30 NULL
If you see, above XYZ is getting duplicated based on the join. This leads to wrong sum number.
Refer:
W3School LEFT Join[
^]