Taking a look at the photo you will see the Aperture Actuator pin. When the lens is rotated this pin pushes against the Nikon lens aperture actuator until it comes to a stop and won't rotate any more, this will be full open f/2.8. In-between it is stiff and will stay put.
Rotating it the opposite direction the set screw stops the lens and the lens will be at f/22.
The aperture actuator pin and set screw set the rotation limits.
Three shallow holes are drilled and filled with white, green and red paint, these are the aperture indictors.
That's all there is to modifying this Fotodiox lens mount adapter. A small pin, set screw and indictor.
http://indiavrtours.com/pic/lens_adaptor.jpg
