Take your fingers and turn that brass plate all the way to the right until it stops. Then place the chrome knurled ring-plate with the red line on the edge so the red line is close to the 4:00 O'clock position. That either 04:00 for you of course. That knurled plate can only be put on in two positions since it has an oval hole and not a round hole. After you have the chrome, knurled red line plate install you can then set the ISO/ASA plate with all the number on it in place. Line the red line up with ASA/ISO number 25. Then thread the retaining screw in and tighten down making sure the red line remains lined up with the number 25. You may have to loosen and reset the number plate a time or two to get it right because it will have a slight tendency to shift as the top screw is tighten.