Where is my data when I backup to Google Drive?
The Google Drive includes a special hidden folder that your app can use to store application data. You cannot choose the location by yourself.
The 'Application Data folder' is a special folder that is only accessible by your application. Its content is hidden from the user, and from other apps. Despite being hidden from the user, the Application Data folder is stored on the user's Drive and therefore uses the user's Drive storage quota. To find out more, review official documentation (which gets tiny technical so beware :)