Step

This scrollbar allows the step size of the smoothing window to be
changed. The step is the distance that the window is moved between
smoothing calculations It can be set by the plot window distance or
number of points.

Smoothing is done on the view of the data in the plotting window, for
example, it will work on an arbitrary projection shown in the tour.

In terms of distance the smallest width provided by the scrollbar is
min(100,width/10), and the maximum is max(32768/9~3641,width/3) .

In terms of number of points the smallest is 1 and the largest is
width/3.

The step size does depend on the actual window size so the two
scrollbars don't always work independently.