Data Usage Doesn't Add Up

[AC Question]

So I was just checking my data usage and the total amount used seemed higher than it should be in comparison to the individual app usage. I have a 10GB plan from the 3rd of each month to the 2nd of the next month. It said I had used 6.60GB so I added up the usage from each app (replacing all the <1GBs with 1GB so the total would be a bit higher) and it still only added up to 6.04GB.
Does anyone have an idea of why almost a whole extra GB is being used up but not listed?

 

[B. Diddy]

Welcome to Android Central! The system itself might be using some data that isn't reported in that list.