Left column / Media: file size divided by duration
Right column lists the individual tracks (video, audio, subtitles); bitrate information refers to those individual tracks.
Actually neither very much.
The really important bandwidth values are determined by Plex during the nightly maintenance cycle.
Open the Plex media info XML, then look for the requiredBandwidths properties.
Just like above, there are numbers for the file as a whole, as well as numbers for each of the various video, audio, and subtitle streams inside the file.
