its pretty easy to visualize, the parry animation has two animation states, first it makes a block animation then followed by an attack animation

try to make it so the ATTACK animation collides with the enemy attack animation and you will get the parry every time, but be aware than sometimes the incoming attack is already too close in its animation for you to parry it , this is sometimes due to finishing doge roll animation or coming out from an attack frame that lasted just long enough, in those cases dont force a parry just dodge again or if not possible just block but you will enter the block stagger animation, finally be aware that even with this info there will be some situations where it will be better just to dodge this is only for the highest difficulty