It should be 30mm, however, the easiest way to test (and similar to the focus bar method) would be to;
1: Do the platform height calibration.
2: Make a mock job and either send it to the machine or USB drive.
3: Start the job on the touchpad and choose manual thickness.
4: Touch the 10W laser to the platform and hit next.
5: When the laser moves up for you to set origin, tap the back button all the way back to the home screen.
6: Read the machine height from the control screen, that should be the Z height you need to subtract from your home height. 