Well I'm sure you could. And I'm sure I could. But I didn't, that was not reset for the whole 50 mile journey, which I said. No maxidot doesn't show the miles, I don't know of one that does show both values at once. I suppose I could have photographed the main screen, but TBF having just arrived at work and simply being impressed with the numbers, I wasn't thinking that three years later someone on an internet forum would be calling me out. Be skeptical it's your privilege, no skin off my nose.
For a good portion of the motorway part it was M42 with the smart motorway restricting me to 50, so the figure was looking pretty good. So for the M40 part, I set the cruise to 56 (90 kph) as it tends to be where fuel efficiency is best, because it's the speed the official tests are done at (or one of them). You can be skeptical about that, too, I might have set it to that at the same point I might have reset the trip. Except I didn't.
In terms of how the display compares to real world, I can't say as ICBA to keep track of exactly how much fuel goes in and the miles I do. But the OP was showing trip computer info, and that's all I'm showing. At the end of the day, this thread is only a bit of fun isn't it? I wonder how accurate my V6 vehicle is when it does max 27MPG according to the trip? Could be under 20 MPG, scary, but then it hasn't been filled in 3 years!