Actually Shedinja does 50 damage times the number of counters, not damage. So it would be (50 x 18 + 90) x 4 = 3,960. With the Puzzle of Time/Dowsing Machine combo, you can add 200 damage (4 additional Plus Powers from Puzzle, 5th from Dowsing = 50 damage x 4 weakness) to make it 4,160.
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