That's one of my favorite things.
If I've just been putting around town doing errands and idling at lights, the mileage is low. Then as I get out on the highway and cruise at a steady speed, it improves and the range goes up. I've left the house showing 410 mile range, gone on a lengthy Sunday drive, and pulled into the driveway an hour and a half later showing a 408 mile range.
I joke with my wife about it, when the range jumps up, that eventually gas is going to start spilling out the filler neck. Especially when I fill up in the mountains and reset and then the next half an hour is largely compression braking.