Prapan-Chopashama means quietude or cessation of the 3 universes. Stool, sukshma, karan, prapan-chatrayam mean negation. What needs to be negated? The error called the snake. If there is no snake that you see there, no false snake, there is no need to negate anything. No need to see the falsity of anything. It's not there. And that which is not unreal, need not be negated.
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 7 (Part 2).