This exercise aims to help in two key areas
The second of the lateral wrist movement exercise builds on the basic position shift that we learned previously and helps us to locate positions on the fretboard purely through proprioception, that is knowing where your hands are in space without having to look at them.
The first exercise developed a clean relaxed position shift, this one takes advantage of that to get you comfortably changing position up and down the neck. In addition you'll build some muscle memory that will help you find the note with your left hand simply by referencing it proprioceptively. That is you're motor and sensory systems will remember the distances between notes so that you are less reliant on looking down at the fretboard.
Play the D on the 7th fret third string with your first finger and then the C two semitones down on the same string with your second finger, moving from the 7th position to the 4th. There are a number of things to note here:
Do this exercise slowly at first and gradually increase it until you notice any tension in your hand, arm or shoulder. Slow down just enough so that you can stay relaxed and do the exercise there.

The left hand exercises aim to:
We are concerned here, as has been mentioned, with our relationship to our instrument. The plectrum introduces a new element into this equation: a small, flat triangular piece of plastic. To use it well it has to become a part of your hand.
Up until now you've been concentrating your focused awareness skills on various parts of your body. With these simple exercises you'll learn to extend that focus to the part of the plectrum that strikes the string. Make sure, as always, that as soon as you notice any muscular tension you slow down and reassess your approach.