For example, if she decided to “cut the opponent’s right arm”, she will take any means necessary to cut off the right arm.
It will become the most ideal slash for the situation, “a stroke with no wasted movement that bends time and space to its needs”.
From the targeted opponent’s perspective, the super genius has entered their zone as if she was locked on to them with a laser sight, causing them to think “This chick is aiming at my right arm like hell! She’s itching to cut it off! I know she’s going for it, but I won’t even bother blocking, because I can feel she’s gonna cut it off no matter what I try! HEEEEEEEEELLLLPPPPP!” Super scary.

It’s the power to make “the means necessary to accomplish one’s goal narrowed down to one single means”.
One could say they are extremely special Mystic Eyes that limit the infinite possibilities of the future into “one single” result.