Widget is used to remember the result. You can subtract and add points.
To see the widget running on the home screen, add the widget there:
Press the Back key (in the upper-right corner of the emulator device) to return to the home screen (showing a watch face).
Swipe the home screen right until you see + Add widget. Select it.
Swipe right until you see your widget application. Select it.
More informations about widgets: https://www.youtube.com/watch?v=PTfne3rOF6g