It's worth remembering that these progams measure throughput only at the network interface on the PC on which it is loaded. This of course is fine if you're only using one PC.
If you have a multiport router and a few other PCs, NetMeter will also record up- and download activity to and from the PC to other PCs on the LAN, (and even to the printer if like me you have shared printer hanging off your router); it doesn't know how to differentiate between that and internet traffic. Nor does it allow for the ATM overhead which is included in your VMBU.
If you want to record usage between your modem/router and the internet, (i.e. at your WAN interface, the same as your ISP sees) you'll need a program like Kiwi SysLog or PRTG (if you're using Windoze).
Some routers will also have a syslog program provided which can be configured to record upload/download activity, and/or are SNMP-enabled to allow similar monitoring.
Linuxes often have a syslog daemon which will utilise the latter too.
(As it happens, I happily just use NetMeter too. After investigating and trying a lot of the above, it all seemed too much faff to bother with ... )