Well, Chrome used 9.9MB, and Malwarebytes used 0.9, so there's 10.8 of the additional 11.6MBs since 3:25PM. So the other 0.8 is spread over a few things. The Status Meter, McAfee, Accuweather, etc. 11.6MB data over two hours and fifty four minutes is not much usage at all. It looks fine.
No. It's not going to blow up. LOL. Everything right now looks good. Since 3:25PM you've used very little data.
Just keep an eye on it. Unless it starts rising drastically, you are fine. Remember, that 300.7MB is your total for the day, not since you last checked it. That's the total since 12:43AMthis morning (your left slider wasn't quite on 12:00AM, but you weren't on then, anyway, as you can see). When you look at the "Day" tomorrow, it will be from 12:00AM to when you are looking at it.
Also, even when you X out of the program on the screen, it's still tallying. It doesn't shut down. It only shuts off if you go to the icon in the task bar, right click it, and click exit. But, don't do that. LOL.
Again, everything looks fine right now.
Also, Old Labs indicated that the Windows 7 updates today were about 175MB, and your Host Processes is right at that, so that's something that you won't have every day.
So, in reality, without the updates, your usage was about 125MB so far today. That's not bad at all. Heck, I probably use at least twice that every day that I'm on, not counting any Windows updates that I have.