This is not a typo but rather a reference to event #54, Moqtada al-Sadr, from the base game. This event reads:
Play if troops in Iraq. Place Sadr there. It is an active cell but cannot travel or be disrupted. If the cell is removed, remove the marker from the game.
So the priority under rule 13.3.2 is to remove the "Sadr" marker (which counts as a cell) if possible.