A picture is worth a thousand words, the Jeti box helps.
On that screen, don't set the G-force, it is a calculated value, described in my post above. The value is not useful with G-force I and D set at off. When you turn on I and/or D, the timer will calibrate. Again, noted in above post. During calibration, you will observe rapid blinking for approximately 3.5 laps, which indicates the need to fly level for successful calibration. Then the G-force value will be calibrated by the timer and give you a value. That value will likely be in the 3.3 range. If you then change the G-force number with the I and/or D remaining on, then you don't get a new calibration automatically but the timer will use the G-force that you entered. I do not recommend this as you can end up with the timer using a lot of battery trying to get to your number. It can have a purpose, but it will take a lot of trial and error to get it to be helpful.
G-force is calibrated automatically if you change base rpm. You will know if it is calibrating by the initial fast blink for 3.5 laps.
At the G-force screen, to add more increase rpm, or a larger decrease, use the I and D functions on that screen, not a manual change of G-force.
You can turn off I and D and the G-force number will still show, but it is not being used if at least I or D is 1 or more.
I suggest that from you are, you turn on I and/or D to 1 and let it calibrate to see how it works. Observe the rapid blink and see that you get a G-force value of around 3.3. That could be off a bit based on your line length and lap time. Try a short flight to see that it works, then change base rpm up of down a few clicks and see that it recalibrates, and that you get a different G-force. If that all works, then try 5 for I and D, and if that works you can then choose your settings.
But be careful to check your flight time and battery usage. It is easy to forget that you are on a short flight time and begin a pattern. If you do that, you may be grateful for the blinking light. It is a thrill to get partway through a pattern and see the light stay on. At least you have 2 laps to figure out that you are going to land, or arrive. Worse is to get low battery because you didn't keep track. I speak from experience :-).
I hope this helps.