DevOps, CI/CD and Automation

hi,
i am creating group by reports with serial numbers. i use the
following code to generate the serial numbers using a formula
column:

function SNOFormula return Number is
SNO NUMBER(5);
begin
SNO := :SNO + 1;
RETURN(SNO);
end;

I am able to acheive the required output with the above code in
the case of Normal Tablular reports. But in the case of Group by
reports, the output goes as follows:
for example:

sno,groupno,empno
-----------------
1,g1,e1
e2
e3
4,g2,e5
e6

Any way out?. pls help.
Regards,
Prabhu S