This is a good cover for twisting the hand with the dagger. Also from taking this grip I will bind you well and if I place my right hand under your right elbow I will put you to the ground, so well do I know my art.
As a note on translation, the text actually says to place your right hand under your opponents right knee. This is not only not what is depicted, but it also makes no sense. I have made the assumption that it is a scribal error and is intended to say elbow.
This is a neat defence which puts an extreme twisting pressure on your opponents right shoulder. Practitioners of karate will recognise this as mawashi uke.
As the 1st Master you have defended against any downward attack with a hooking block. You caught your opponents attacking wrist with the hook formed between your own wrist and the base of your thumb. Then you rolled your hand over, catching their wrist and completing the master play.
As the 2nd scholar, you simultaneously pivot your hips square to the opponent. With your palm up, use your right hand to cup your opponents elbow. Wrap your fingers around to give a firm but gentle grip. Ideally you want your opponents hand directly above their elbow.
Visualising your own hands as being on the top and bottom of a wheel, turn them 180 degrees anticlockwise. Keep your elbows in. You will be mechanically strongest the closer you can do this to your body. Take care, of course, not to impale yourself on your opponents dagger.
You are using your opponents arm as a crank handle. By the time your hands have swapped position, your opponent will be falling to your left.
Complete the throw by holding your left hand still. It should now be at the bottom of your circle, and you can now safely bring it right in to your centre of gravity. Using that as a new pivot point, keep cranking with your right hand in an anticlockwise direction. Step through, either forwards or backwards depending on the momentum of the situation, so that your right foot is forward.
Your opponent will be left lying on their back, with their head at your feet and a badly dislocated shoulder.