If you load a line made at a different width the display will calculate the amount the line needs shifting with your current implement. As posted, I do not believe it will do fractions of an inch, but it will round by itself. All you need to do is tell it if you are shifting left or right from the perspective of sitting on point A and Looking at point B.

I have a few guidance lines that have been around for a decade that were made at 12.833' (7R22) implement. I have loaded and used those with implements of 15', 24.5', 38.5', 66', and 80'. All I have to do is tell it which way to shift the line. Towards the outside of the field if the current implement is narrower, away from the field boundary if it is wider.