Clockwise puts more pressure on the spring. More pressure on the spring means it takes a higher psi to push the spring. The spring is pushed by fluid pressure. Therefore more pressure on the spring means a higher fluid pressure is needed to move it, resulting in more/longer action in the rear brakes before pressure is reduced. Full master cylinder pressure is allowed to the rear brakes until the piston, held by the spring, moves.
The adjustable valve has arrows on the knob. Clockwise=Increase.
Putting it in backwards would effect operation, but I dont think it would operate correctly or opposite.