The interfaces are ordered by their utilization, taking the Top X.
I'm using avg bps for the charts but I would presume the calculation would be the same for any of the avg charts, what I'm trying to get at is how is the top 5 interfaces arrived at, is it the top 5 arrived at by the avg bps at a specific point of time so for instance when the graph is displayed or an avg of the avg bps over the time frame I'm graphing or something different?
We always use Current Percent Utilization to select the Top XX interfaces. This calculation is the same for all charts, no matter what they show.
If you need to show specific interfaces, you can use "select interfaces" button on the edit page of the aggregate chart resource.