That is odd, and I've seen that too. I think there are a couple of lines of bad programming integrating the roughly three calculators it keeps: current trip average, total current tank average, and the new tank average when you refill. Also impacted by the reset options you choose. Odd, but really doesn't matter much. As you know, the estimate is often off. For me, most often it is about 3 mpg off. But I've had several tanks less than 1 mpg, and one that was 6 mpg.
2018 Kia LX HEV Metal Stream with Advanced Tech