it is however totally dependent on what you type in
Very true...you enter estimated fuel flow, fuel onboard etc at the start of the flight, and it gives you a tally of how much you *should* have left.....
No substitute for a proper fuel guage, though it can draw your attention to a possible low fuel state or remaining range. Ideally it would have a flow sensor on the fuel so it knows really how much you've used...
EA