Neville has re-invented the wheel.
The “book” method of making a final adjustment arose about 20 years ago. At that time people were making two sets of marks as they measured. There is nothing inherently wrong with this, but when the data was sent to the certifier, the question arose “How far apart were the marks when the measurement was completed?” Generally no satisfactory answer was provided, as the measurers rarely recorded the difference. Thus no way of knowing the difference between two measurements was possible.
If this is done, it is necessary to take a reading at the previously-established end point so as to secure a solid second reading. Then one may safely go on to whatever final point one wishes.
It is much clearer to explain when two measurements of the same thing are made, and a final adjustment based on that is done.
Also, when three or more measurements are made, confusion reigns. I remember looking at data from a long-ago New York City Marathon measurement. An adjustment was to be made based on the position of the 18 mile mark. However, six riders had measured the course and there were 18 mile marks all over the place. A clear understanding of what had been done was just about impossible.