Hi Andre,
As per your previous post I am getting that you wanted to create a report with the columns "Total value" and "Time Avg" which are grouped by "Month". And for this you are having the Measure fields as well (consisting values and time fields).
If you wanted to create the report like this then you need to use/create an external variable in the process (as an output variable) which consists calculated values from the fields of "value" and "time" as an "Total value" and "Time avg" respectively, (I think, like you have done with execution time taken by the process) and then add these variables in the Measure tab.
Then in the report configuration you need to use "Group by" with the Month and aggregation function as Count/Sum etc(depends on requirement). After that you need to add those fields/variable (which you have added in the process measure tab) as an column which you wanted to be displayed.
So once you launch the report you can see the report with the grouped by month and with each instances with the Total value and Time Avg fields.
Note: As per default aggregation function (provided by RMP) will work one at a time.
Hope this will helps you.
Kindly let me know if I misunderstood.