The rate of drop only regulate the return fluid back to lift spool and then to diffy housing. The supply flow actually enters the lift cylinder area from a different passage way. the hole in the middle is for return and the hole on the left is for supplying fluid to lift the 3 point. This pic is on 1700 but concept is the same. The very hole on the left is shock relief oil return.
Edit:Just turn the knob clockwise to pinch the valve down and it would come down slowly. If you do it all the way then you cannot lower the 3 point.