I believe the problem has two layers. The first problem was leaving with 5%. That means he didn't have energy to make it to his destination from the start. The second problem showed up when, for some reason, the energy graph predicted 12%. I'm a little surprised this would happen because leaving with 5% means the car already assumes a slower driving speed. There is little potential to driven even more efficient to make the prediction go up so much.
Not only do I find this unsurprising, I find this to be common. It is so common on my trips that I am surprised when it fails to happen. Leaving my place in VA and heading for Rocky Mount, NC it typically starts out showing around 5% remaining. The first 30 miles or so are very back roads. I want to say I get a small boost rising to maybe 8% by the time I reach the highway, not sure. But I know by the time the remaining charge estimate settles down it is usually around 15% or higher. I typically reach my destination with 12% to 15% remaining.
That is one of my major frustrations with the car, the inability to plan on reaching chargers at least 200 miles away even though the car has a range of 286 miles.