This morning, I received an interesting email from a future student about this picture:

I have received the manual for the Assembly course. Please let the instructor know ahead of time before the commencement of the training. There is a major mistake in the illustration shown on page 28 of the textbook. Width and Tab references are marked incorrectly. I had to figure this out by trial and error- big waste of time. I finally got it to work.

And he is right!