You've got the right idea, but I think your numbers are off. If you shorted 25 BTC at $200.00 would you not be credited with $5,000? So when the price rises to

You've got the right idea, but I think your numbers are off. If you shorted 25 BTC at $200.00 would you not be credited with $5,000? So when the price rises to $400 you would have to buy back the equivalent amount with $5,000 of your own dollars and $5000 from the original short.