The claim was it "contains every 15 seconds audio recording you can imagine. Every single one.". Which is bullshit, that's like saying this program contains every single literally work:

import sys

print(sys.argv[1])

It's just adding a layer of encoding on top so it feels less bullshity, something like:

def decode(number: int):
  out = ""
  while number:
    number, letter_index = divmod(number, len(string.printable))
    out += string.printable[letter_index]
  return out

That also does not contain every possible (ASCII) book, it can decode any number into a text, and some numbers happen to contain texts that are readable.