Seems noby else has ever had this ? Still shows 1.5x data shown on windows so which is real ? Please let me know if there is somewhere more specific to ask this.

I am not a Windows user as I use Apple. Not sure how a device (PC) connected to a router can see all of the traffic on the router. I would think you would need to monitor the traffic at the modem. Other devices even when not in use can cause traffic. For example, those voice controlled devices are always listening and phones and tablets checking for email.

Thik you are right, and thanks again for replying. I assumed the router uses some additional data just by waking up and logging onto the mast so the pc can connect. I reset all data counters, windows and router and now seems just fractionally more used by the router. Sadly my phone sim in the router has no way of checking what it thinks it has used :( Here in France mobile cards are a nightmare, most have unlimited calls to french phones but lots of convoluted inlimited offers to others. So call any country's mobiles but not landlines. Some do landlines but only europe. I am using this as an experiment alongside my fixed internet(which is very bad) and will switch over once I have the 4G running well. No problem with data usage as such, I seem to use 25gb/month so I just need to know it will not be much more than that because of 4g router.