You aren't applying an aggregation in your FCST vs PY field.
So look at what you're displaying in your report; You have SUM(earned hours fcst) and SUM(earned hours PY)
Yet in your calculation your just doing
earned hours fcst / earned hours py
So when you include that in your report with the default aggregation of SUM, it's going to do SUM(earned hours fcst / earned hours py) which is why the result is wrong.
You need to change your fcst vs py field to ;
SUM(earned hours fcst) / SUM(earned hours py)
Thanks a lot for your inputs.
First I tried SUM(earned hours FCST) / SUM(earned hours PY) as you mentioned and I get below error then just (earned hours FCST) / (earned hours PY) and the result was wrong.
I tried today to calculate the sum in separate fields:
then I use a new calculated field.
Strange is because now it works ok.
The original error is appearing because you're trying to apply a SUM to a field which is already aggregated. If you wrote the formula as I originally described then added it to the measure values list it would look like AGG(yourfield) instead of SUM(yourfield) and it would work OK.
You've effectively done the same thing just with a couple of extra steps, but next time you could just do sum(x) / sum(y).
Thanks a lot Tom, now I understand your point.