Good question Tank... not sure of the answer though, except one would assume that 1% in the middle of the range, means that if you get on the high end or low end it would be greater than 1%.
Personally, I've had the digital gauges and they haven't been accurate. But maybe I just bought the wrong ones

. However, I would say they are consistent. So even if they are wrong, at least they would be consistently wrong

That can be a good thing as you could go and get a calibration done to see how far off it is and then just remember those numbers when you go to use it. Personally, I have too much other stuff to remember, so I just want a good/accurate gauge that I don't have to worry about. So far the Blue Point has been that for me... time will tell I guess.