Monitor ALL network traffic by app
In the screen shot you are showing the Network usage numbers are excatly the same 27.3 MB. 

The individual network usage per application (coulomb) are current (active) numbers, which are much smaller and are not meant to be added manually to find out the total usage. OS X does that for you in the table at the bottom.

The Table at the bottom is showing the total usage for all applications and it is cumulative (for 7 days) or between restarts which ever comes first.

I did the test:

Data Usage before restart.



and Data usage AFTER restart: