Separate the advance plate from the coil plate by removing the three slotted head screws. The rotate the advance control pin into the advance plate as shown in the modified version of your image. This will fix the advance plate to the coil plate negating any movement of the mechanical advance mechanism.
Make sure a all is properly lined up and re-install the three screws. Put the dizzy back together and it's done. Re-set the ignition timing and all should be good to go.
This is a lesser known feature of the Bosch dizzy used in the X.