You did not exactly follow my steps ...... you missed step #2 ... Select the "Apps" Button.
Your usage period as defined by your slider settings is rather large at 6 days but culprit is right on the top.
Host Processes for Windows Services ..... 2.1 GB ..... that is 2100 MB of data used sometime within that 6 day period.
Short version .... Your Operating System, Windows is eating your data like its going out of style.
Do you have Windows 10 ?
To be more exact ... what Operating System are you running ?
Well, lets see where Host Process for Windows Services went:
Here is mine , use it as a guide:
Same settings as your previous EXCEPT:
SELECT THE "APPS" TAB
Then, in the list of programs/processes find Host Process For Windows Services ...... and CLICK on it (mine has a red box around it)
After clicking on it the large window on the right will display how much data was used ... CLICKING on one of THOSE will display a popup with the IP address of where the process connected to.