Issues with Voltage Divider Calculation

Hi, I’m having some real frustration learning how to do the Power Setup on my drone properly.

When first test flying my drone the battery percentage was all over the place and it landed after around 90 seconds in the air, then the battery percentage jumped back up once the rotors had stopped turning so my next step was to setup the battery properly.

When measuring battery voltage there is not more than a 0.01 volt difference between my multimeter reading of the battery voltage and the PDB’s reading showing in QGroundControl. I would be happy to leave the -1 value in there but am confused by a few online videos I’ve seen where people have a number between 10 and 20 in there with no explanation - are voltage readings on some boards that wrong or am I just confused?

Also, if I enter a dummy value in the voltage divider, say 10, then use the calculate window with a PDB voltage reading of 16, and enter 16.5 - I can then click ‘calculate’ repeatedly it just keeps incrementing the new voltage divider value. Shouldn’t this just do one calculation and that is the answer? I am quite confused by this.

I’m using a holybro RPi CM4 baseboard (PX4 1.14.0) with a holybro PM03D PDB and a Zeee 4S 6500mah battery, QGroundcontrol 4.3.0 on ubuntu 23.10 if this helps.

Many thanks.