Pete:
I am not clear as to why you are differing, but a perhaps a detailed example of the overshoot correction will clarify matters.
A measurer finds that he has taken a wrong turning and needs to go back several hundred feet to get back on course, but he is not sure exactly how far. He does not need to take a reading from his Totalizer, but he does needs to select a rim reading. Say he selects 0.1 because it is easy to remember. He then adjusts the wheel to this reading and turns the bike 180 degrees about this point. He selects decrement mode on the Totalizer, rides back until he is comfortably on course again, and stops at any point with a rim reading of 0.1. He again turns the bike 180 degrees about this point. Finally, he selects increment mode and rides off along the correct course without reading the Totalizer. His future readings will be exactly the same as if he never went off course.
Some measurers will find the above hard to believe, so I should have liked to have given a demonstration at the Honolulu Meeting. Regretably, I will not now be attending.