My data usage jumped a ridiculous amount last month and I'd love to monitor the data use at the device level. Anyone have tips on how to do this with an Arris router?

Mine jumped significantly and when I did start tracking it from my router, the discrepancy between my router and Cox's Data Meter was 312%. They are blaming the tracking tool on my router; but according to my router documentation it should be 10 - 11% (mostly what we used to call "handshakes"). Not over 312%. Cox wasn't even interested in investigating it.