From just the superficial observations of how it’s acting and comparing it to how a Prius or my old ice cars goms work it seems rather straight forward. The basic two numbers it’s using is current state of charge, how many kW’s are currently available. The second is the current kWh per 100km. Guessing on how many km are left on a charge from that point is a very easy calculation. If 50% soc remains that’s 32kwh of battery. If you’re getting currently 15 kWh per 100km then you have 213.33 km remaining. Now the reason why the GOM jumps around so wildly is because your current usage rate is not consistent and how it’s calculating your current usage per 100km has some variability based on real world data. Most likely it’s a formula of several data points: your performance average of the last 5 or 10km runs or partial runs. Your last 5-10 minutes of driving and a total average over the last say 1000km. The set of data points would all be constantly changing causing your current usage attempting to create an accurate average of your usage. A generic daily driver doing the same route over and over will result in a calculation that’s heavily unchanging where as an erratic driving doing lots of things and having multiple people will have a formula that’s wild and constantly changing. But the basics of SOC divided by the current kWh per 100km is probably all the GOM is providing and the kWh per 100km is a snapshot of a **** of stuff averaged out. The Prius used to show you graphs of the sub categories of your performance that was being used to extrapolate your GOM rating. It’s too bad the data formula isn’t laid out too as I like all that extra data.