I must have received a different scale, mine started at 1″ so setting the stop to 24″ gives me a cut piece that is 24″+ 1.38″ (the gap between the arm and cutting grove).

Also, on another but related note, the design/screws provided with the arm let the user fasten the arm in such a way where it’s not square. There is no sure 90 degree angle that the hardware sets itself into when the screws are fastened. I had to use a woodworking square to adjust the squaring arm to be perpendicular to the cutting groove.