Canon Auto-up

I recently acquired a Canon Auto-up attachment for my Canon IVSB2 with 50mm 1.9 lens. I know you place it over the front of the lens and tighten the screw to hold it in place, then focus as normal with the rangefinder. I imagine that the working distance is from 22" to 44" and everything in between.
I have no instructions with it so I am not sure how to compose or frame the picture once I have it in focus. Looking through the viewfinder, is the picture I see framed the picture I will capture or is there something I need to do to take into account the closer focusing to determine what part of the frame I will be capturing?

Once you mount the Auto-Up, operate as normal. Viewing and focusing is using the camera's viewfinder. The big magnifier window will show you the correct field-of-view.

Jim B.

Thank you