Data usage are stored in which location?

Hi all,
I need to know where each application "data usage" are monitored in android.
I am planning to test(hack) an application by having tie up with that application team.
For that I need this information,
I am able to see UI of each app usage in settings
Watsapp - 2mb
Hike - 5 mb etc
But I need the file where this information are stored.
And is there way to edit that file in rooted mobile.
Thanks in advance.


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