usage issue

[#1]

Hi,
just had my broadband activated today (fibre) and have a query about usage so maybe someone can enlighten me.  Basically I have signed up for the 120 GB monthly package but have noticed a pretty major discrepancy between what the Plusnet usage monitor shows and what my router's statistics indicate.  I have been online now for ten hours and 15 minutes and according to Plusnet I have downloaded 1.75 GB of data but according to my router I have downloaded 1.42 GB during this time period.  While I would expect some fluctuation between the figures; a discrepancy of around 300 MB is a bit much.  If multiplied over the course of a month then it is going to seriously eat into my 120 GB allowance.  Has anyone else noticed this? 
So my question (s) are:  Have I missed something? Are the Plusnet usage monitor and my router measuring different things?  If, however, both are measuring the same thing, then what would account for a discrepancy of around 300MB? I just would like to think that if I am paying for a 120 GB package that that is what I in fact get.
I have also raised a ticket with support (and sent screenshots) but have not heard back as yet.
Many thanks
Graham

[#2]

Did you add the upload usage too? As with PN it's up and down usage total.

[#3]

Hi, i didn't but upload was 54 MB but that still leaves a fairly significant difference between what Plusnet's stats say and what the router tells me (not in my favour incidentally!).
graham

[#4]

Background traffic that your router isn't passed through to your LAN is unlikely to be included in your router stats. I also have no idea what logic is being used to collate this figure. It could be that it's recording Gibibytes rather than Gigabytes (1.75GB = ~1.693GiB). Still some way off the 1.42GB you're quoting but worth considering nonetheless. As RPMozley has alluded to, we count upload traffic too. If you notice any large discrepancies in the future then let us know and we can check things at this side however I'm fairly confident the figures will be accurate. Would be interesting to see what a local bandwidth monitor like Networx tells you?