You can learn something doing it trial and error by half turns and observing the effect. Keep count so you can always go back to where you started.
Or you can imagine it in your minds eye. As you correctly point out increasing the length of the housing effectively shortens the inner wire bringing the RD inboard, turn the barrel so it turns upward or out (counterclockwise).
BTW - in case you never learned the right hand rule for screws here's a handy way that will point the way in all situations. Make a loose fist with your thumb point out, like for hitchhiking, with your right hand. If you turn a RH screw the way the fingers point, the screw will move the way the thumb points. Anytime you're in doubt put your right hand near the screw and go. For left hand screws use your left hand.
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