Translation
What is said here cannot be done every time. I know the counter to the scholar who came before me, who is a great fool. I know how to do it so that my leg is going to stay, and I do it by putting the dagger in his face to show that he is both mad and foolish.
Interpretation
Against your fendente attack, your opponent has defended themselves as the 9th scholar of the 1st master. They have jammed the attack with their left hand using a hooking block, and are trying to scoop out your right leg with their right arm.
They will need to drop their weight down very low to attempt this, as well as swing their arm strongly across the front of their body. Step back with your right foot. As you do so, grab your opponents jacket behind their right shoulder and pull. This will exaggerate their movement, tipping them off balance. This is the moment shown. Your opponents structure is completely disrupted. Overstretched and twisted, they will be stumbling forward to avoid falling forward onto their right shoulder. The cover they make with their left hand will lose all its strength. Turn your hips to the right, pushing your dagger through their collapsing structure and into their face.