Minor moral dilemma

Well, I have this new cycle computer, see, (you'd never guessed?) and took the bike over one of my standard routes. And the new gizmo measured out 15.63 miles over a course that the old one measured at 15.2 - 15.3.* Now, do I adjust the calibration of the new one, or do I say the old one was wrong and I've just added hundreds of miles to my lifetime total?

*New gizmo measures trip distance to .01 miles, old one to .1 miles. The higher "precision" is laughable, as you get more variation than that with a couple of pounds of air pressure in the tires....

15.?? miles, 1:03:30