Translation
When I give you my thumb under your ear, you will feel so much pain that you will go to the ground without a doubt. Or I will make some other grip or lock that will be worse than torture. The counter that he can make is the sixth play against the fifth, where he puts his hand under the elbow. That can be done to me as a counter, without doubt.
Interpretation
From the position of the master play, your opponent has grabbed your right forearm and left shoulder. By making a volta stabile, they are attempting to make a forward twisting throw, pulling you down in front of them.
Slide your right arm over your opponents left shoulder. Wrap your fingers around the back of their neck. Push your thumb into the neck between the earlobe and the corner of the jaw. Straighten your right arm and allow your opponent to pull you onto them. This is the moment shown in the picture.
Your thumb is driving into a very sensitive pressure point. The more your opponent attempts to throw you in this direction, the greater the pain they inflict on themselves, and the more they will disrupt their own balance as a consequence.
Step through with your back foot, continuing the momentum which your opponent has begun. Push their head forward and down as you do so. This will throw your opponent face down on the ground in front of you.
Be aware that your opponent may attempt to counter this by changing the direction of their movement to an anticlockwise turn. If they can successfully switch feet while lifting and catching your left elbow, they will throw you same as the counter to the 4th scholar of grappling.