Top 10 Average Time chart data not matching list

[bbrooksux]

Frame of reference, we're using Cognos 8.4 on a relational data source, currently working with SQL (but will soon expand to a separate Oracle instance, not that that part really matters -- hopefully).  Now to the issue:

I have a list report that is fairly straight forward.  There are 2 columns that are grouped: Queue and User Name.  The last 3 columns represent time interval calculations that are time A minus time B for the first 2 column grouped items, but shown as Average, Minimum and Maximum values.  The list appears to calculate everything just fine and when checking the data, all numbers tie out. 

The problem occurs when trying to build a Top 10 Average Time chart based on items from the list, where the X-axis would show the User Name and the Default Measure would be the Average Time.  Some of the times in the chart do correlate to what is shown in the list, but others are way off.  I placed a support ticket with Cognos and their response was that "it's incorrect to assume that the results from a list will appear the same in a chart, but that a chart is a graphical representation of a crosstab and that I should obtain proper results in a crosstab to get the chart to work."

Sounded like a pretty bizarre thing to recommend, but I thought I'd give it a shot.  When trying to build out a similar crosstab, lo and behold the average time was still "off" in some instances.  Looking at the generated SQL of the crosstab, it's showing an XSUM and XCOUNT, but no XAVG (like I'm seeing in my correct list). 

So any ideas or thoughts on how to get a ranked/top 10 average time chart to work based on results from a list?