"The spacing between the pins affects how close to the end of the stock the center finder can be used. If that is a concern, the spacing should be only slightly larger than the width of the stock.
........the device is twisted on the stock until the pins touch the sides which puts the hole in the middle of the stock. A pencil marks the stock through the hole. Drawing the device along the stock makes a line if that is desired.

The take-away here is not so much the device but the method of construction. Not as accurate as my use of a DI to lay out the holes on my metal version but plenty accurate enough for woodworking. "

This is standard for Mr. K and a limited number of folks, wish it was more universal.
It's not easy to visualize without prior experimentation and some failures. Increasing that ratio depends on observation and suitable records. Like many tools, applicable to various types of work.
BTW, the tool is seen on different workbenches too. First I saw, a gunsmith used it centering sighting beads on a shotgun rib.