How do I know. I went through the same thing about a month ago. When I did my speed, I lightly taped the tip of the needle to the gauge face and rested the other end on the pin. When I hit the speed I pushed it on lightly. Do not push it too hard, it will rub against the face. For RPM, just sit in a parking lot and use the reset trick to find RPM. I set my speed a little higher for a fudge factor. Showed 55 mph and I went with 52 or so.
List of test buttons.
Breakdown of some of the functions:
1 Press - Shows a Gauge Sweep
2 Presses - shows all 8's on the LCD (LCD TEST)
3 Presses - illuminates all the bulbs on the dash
4 Presses - displays hexadecimal value for ROM level
5 Presses - Displays the hexadecimal value for EE level
6 Presses - Shows DTC Troubleshooting Codes (Nothing to worry about though)
7 Presses - DIGITAL SPEEDOMETER - MPH
8 Presses - DIGITAL SPEEDOMETER - KPH
10 Presses - DIGITAL TACHOMETER