That range can change as you drive both up and down (and you'll see it change if you switch to say Eco Pro from Comfort), but I do not know of any way to reset it to any default value. Keep in mind, it is really a guess. Often, the temperature in the morning will be lower than when you stopped the night before, and that can affect the range calculation. The car doesn't know how much or if it will warm up. While some ICE cars do show you an estimated distance to empty, those are only a guess as well, so the i3 isn't any different in that respect. Your current driving and watching the battery level are the most valid indications. You can reset the average miles/Kw readout, and that would give you a good idea of how you are doing on the current trip.