The info displayed on the dashboard can get a little "wonky" sometimes.
Things to try:
Try another browser
Do a hard reset of the modem by powering off the unit, wait 30 seconds and power up again. (remember to do this at either the wall plug or at the power brick, NOT the plug at the rear of the modem)
If that doesn't work the forum Mods will have to address your display issue.
Be advised that currently the newly updated "history" display on the dashboard has some errors in it that are being worked on so discount that for the moment.
In the end, what "counts" is what is being charged against your data allowance and the best display for that is the dashboards "at a glance" meter so it is essential that the display problem you are having be addressed ASAP.
As to losing data:
It is ESSENTIAL that you simplify your network and the number of possible connection points during the troubleshooting phase.
That will start with connecting a single computer directly to the modem and doing a "Modem Isolation Test" that will rule the modem using data on its own in or out,
To do that, follow these steps:
While you are doing that it is recommended by many of us here in the Community to install a free program called Glasswire that will track data usage on the single computer it is installed on.
Glasswire may be found here:
https://www.glasswire.com/help/You may be very surprised at the number of background processes running and connecting to the internet without your knowing it.
My suggestions for setting up Glasswire are as follows:
(click on picture for larger image)
The following may help you understand the results: