I’ll try to add to Ken’s post with a little user experience. My use of force terms may not be good engineer-speak as I don’t know that language.
If your timer says G-force in a window, it is likely a v6.4. The V6.5 has more G-force options showing in the window. If you just turn G-force on to its lowest on setting, it will then show you the outward force that you are flying with, as the number of “G’s” equivalent (after calibration). In addition, you will notice that you get a rapid blink of the light for about 3.5 – 4 laps as it calibrates to find that number. Fly level in those first laps until regular blinking. When you are directly overhead, the plane is pulled down directly along the lines with a force of 1 G. So, overhead the force that the timer shows for level lap is decreased by 1 G. At some value of outward force less than the calibrated, the timer will add rpm based on the amount of G-force selected. That amount is preset in the timer. At some point in elevation, there is enough downward force along the lines to turn on G-force. In real flight conditions, speed may also decrease as the plane climbs and give further decrease in outward force/G-force. G-force may come on in the 45 – 50° range and then be active above. Meaning it may be on at the tops of some horizontal maneuvers. In moderate wind, G force can add or subtract rpm in level flight if the wind pushes the plane up wind, of pulls out enough downwind to exceed the force change threshold. After you understand calibration and the G-force number, it is easy to adjust the G-force setting to fit your style. 5 - 10 is a reasonable starting value.
Nose up seems to come on in the 20° nose pointed up range and then goes off at less. Not elevation, but nose point angle. Nose up does not care if the plane needs a boost for acceleration or force, it just comes on with the angle.
Of course Sensitivity settings also enter in. You can turn off Sensitivity and learn nose up and G-force as already mentioned.
Hope this helps.
See the manual here
https://stunthanger.com/smf/gettin-all-amp'ed-up!/fiortti-timer/msg660554/#msg660554a pdf in reply 116.