I have no answer...but experiencing the same thing. I'd like to be able to track usage by device in my home...so that I have an idea of which family member is causing it ....or is it even accurate.
It seems to be accurate, but Cox only offers a daily tracking of total usage at https://www.cox.com/internet/mydatausage.cox. Video is the overwhelming culprit due to the large amount of data transfer needed and the higher the resolution, the worse it gets. We stream a fair amount of YouTube but didn't and don't have a usage problem as long as we avoid high definition that really isn't needed for computer viewing.
