This signifies that the user has ripped all six physical discs in their entirety. A standard "Immersion" rip might only take Disc 1 & 2. The "6CDRi" means you are getting the complete time capsule: the demos, the live agony, and the alternate universe versions.
What I can help with instead:
Here is a deep dive into why this specific 6CD configuration is the holy grail for audiophiles and what makes the Immersion material so essential. Why FLAC? Why "Split"? Pink Floyd The Wall -FLAC-Split-Immersion-6CDRi...