Same as in all modes, each verifier knows exactly 1 fact to be true; your job is to work out which 1 fact each verifier knows. The only difference with Extreme mode is that you don't know which of the 2 cards that fact comes from.
Remember you are testing a verifier, not a criteria card.
Think of each verifier as having one giant Criteria Card with all the options listed. The verifier knows exactly one of them to be true and knows nothing about any of the other options.