In a nested rollup, display average of lowest level

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I have a chat report that I have rolled up by Agent and then under each agent, I did a 2nd rollup by the Interval type, So I have two areas, Time as Lead Agent and Time in wrap-up separated out under each agent as a 2nd level rollup.

I am displaying the averages for each of those groupings under the agent, but then the report is adding another row at the bottom of all the data for a single agent that averages those interval time averages together.  I don't want to average those times together because it is meaningless and confusing.  Is there any way to not have it do the average of the two averages for the top level of the rollup and only display the averages for the lower level nested rollup?