Translation
This is the eighth play, which counters all the previous plays, but especially the plays of the sword on horseback and the masters who use Posta Coda Longa. When the master or scholar is in a firm guard, I give a thrust or other blow, and immediately he beats my attack aside. When he does this, I quickly turn my sword and with the pommel, I strike him in the face. I then pass from the cover this lends and with a reverse circular blow, I strike him in the back of the head.
Interpretation
Although all the plays of the 8th master of horse are shown with your opponent on the right side, unusually, the counter is shown with them on your left.
Make an attack against your opponent. They will beat the attack aside. The text, as well as the inference from the master play, say that the defence is made from posta coda longa, which would mean that the sword is being beaten to your left. In the picture, the position of the counter masters sword suggests that it has been beaten to the right. In practice, it does not make much difference, although you do get a bigger opening and better flow if responding to a beat to your left.
As the beat knocks your sword aside, rather than struggling to stay on line, exaggerate the movement, and spin it 180 degrees around in a horizontal plane to chamber on your left shoulder. Strike the pommel into your opponents face as shown. It should feel like making a fendente stab with a dagger.
Immediately after you have made your stab, drop the elbow, moving your right hand back in a straight line toward, chambering for the strike. Turn the sword so that the tip continues moving in the same horizontal plane in an anticlockwise direction. If your sword was originally beaten to the left, it would have been moving anticlockwise anyway, so the whole series of beat, stab, strike has a smooth, pulsing kind of feel to it.
Strike forward with your hand, rolling it over as the blade spins around. The sword will wrap right around your opponent hitting them in the base of the skull with the false edge. The strike has a whip like effect. A fast opponent can easily jam it, however it is still strong enough to do plenty of damage. It targets a very vulnerable area, your opponent will be quite distracted, and hopefully seriously injured from the pommel strike, and the surprising angle often catches people unawares.