As is: if a look at the AVERAGE BITRATE (Heartbeat metric) with a dimension (For example Content) the average bitrate of the single content is correct, but if a look at the total the metric is summed and not averaged (so the value is not correct.
Idea: Set Average bitrate as average on Totals.
I believe with processing rules one could take a metric and then create an avg metrics for it.
I used a similar technique to create avg page load speed.
good luck to you.