How to apply a text-display formula on an aggregated value?

How to apply a text-display formula on an aggregated value?

Hi,

I've been struggling with a display issue on a report for quite some time now, but I can't seem to find a solution...

Basically, my report has the X-axis with time-based values (weeks of the year), and the Y-axis with duration values (in milliseconds). Since I have multiple records per week, I want to display the average duration per week, so I have an aggregated function on my duration field, as follows:


I want to display the actual average values, yet I don't want the raw values; I'd rather display something human-readable (and shorter). So I tried creating a column formula with a simple function: sec_to_time("MyDurationColumn"/1000), and use this column formula as "Text" in my report, as follows:


As you can see, it doesn't really have the expected behavior, since it's adding all the values instead (because my custom column formula isn't aggregated, unlike my original "MyDurationColumn"). And when I try editing the report format, I don't see anything that could help either.

So here's my question: is there a way to "translate" an aggregated data value to anything else, in my case to make it more friendly to read?

I would really appreciate your help, thank you.
Cyrille