It does re-adjust as you drive on, my comments were on the initial starting range upon a fill-up.Well, I have another observation for consideration and comment (conspiracy theories?):
I completed a little trip to Cleveland this weekend and flipped over to the range screen. I was averaging 41.6mpg at this particular point in the trip with 28 miles-to-empty and I pulled into a Flying J. I topped-off rounding to the nearest quarter-dollar and got back in. The MID estimated 388 miles-to-empty at start. When I actually got back on the highway it revised the estimate to the (more accurate) 425 miles-to-empty. In effect, it under-estimated my fuel consumption versus what earlier posters have said regarding an over-estimate.
No theories on my part just my observation...