The Range screen shows you how far you could expect to get until your battery runs out. I gather it calculates this based on your riding style over the last 'x' hours or kilometres.
So if for example, you've just rolled down a 2km hill, then the range increases for whatever assistance level you have selected - based on the presumption that this will be the typical amount of assistance that the motor will have to supply.
If you then turn off the path and go bush for a while, you'll see the range drop dramatically as the bike now assumes that you'll be needing this level of assistance from now on.
I've found that in practice, you as the rider generally know what sort of assistance you'll need for whatever the remainder of your trip, so you can actually get a better idea of the projected range by looking at the number of bars of battery remaining. So if you've already travelled 30km, have 5 bars of battery remaining, and the Range is saying 25km, then you know this is probably way less than what you'll actually get. I'd imagine that even after another 20km, the Range would say 25km. Mind you, I haven't ever run the battery below 3 bars.
I can easily commute over some extremely hilly terrain, heavy winds, using the highest level of assistance (Turbo), covering 22km each way, and still have 3 bars remaining on the battery at the end of the day. So I'd expect that on paved roads you should get over 60km, even on Turbo.
To put that in perspective, I weigh about 80kg fully loaded (with backpack), and I also run road tyres - not the standard knobbies.
Maybe a proper range test is in order.