From another thread:
Under the device settings menu you may perform a three
point touch-screen calibration by pressing and holding the yellow
squares until they turn green when prompted, and then hit the back
button when done to save the newly calibrated values.
If your Model-T is so out of calibration that you can't navigate to
the touchscreen calibration menu above, factory default touchscreen
calibration can be restored by pressing and holding the screen anywhere
for 30 seconds and then following the directions on the screen.
This press and hold action must be initiated within the first 30
seconds of powering on the Model-T, so you may need to power cycle the