That’s assuming every shred contained only letters and spaces but no sliced letters. The letters being sliced up actually makes it worlds easier for the algorithm to put things back together. It literally turns it into puzzle pieces that can only go in one place. Even if these were duplicates of one another, if the individual ballots were shredded at even a fraction of a millimeter difference in angle or alignment, the puzzle pieces only fit properly to each individual puzzle, or ballot.