Whichever valves are loose when the mark appears in the window - adjust them. Due to the pressure by the opposite cylinder's valve springs, it will want to rotate past the TDC mark. Then, rotate one half turn and the other cylinder's valves will be loose. Then adjust them and spin the crank a ferw times and re-check the clearance. Don't want one valve ticking louder than the others once you start it back up. You need not go strictly by the cam marks, but by crank position.