I checked my usage today, to find I've used over 1000 Gb in the last couple of days! I'm pretty sure that the Gb unit has replaced the Mb unit when i updated recently.
Not sure what version i was using but I'm now using NetWorx 5.2.8 64 bit, updated on the 14 June. I've looked through all my daily usage for June and noted the dramatic increase in usage from the 14 June.
This is probably you have VirtualBox installed on your computer. You just need to choose ONE specific network interface to monitor in the settings.
As installed NetWorx is monitoring all traffic on all network interfaces, possibly including local traffic or multiple adapters including virtual and dial-up ones and sums it all up. This results in incorrect readings. It may have worked okay in the past, but due to some implications with VirtualBox, this version no longer ignores traffic on VirtualBox adapters.