Around 700 you were shorting - so you were keeping your long while shorting, paying both swaps plus spread?
there's no "swap" on Bitcoin. Feel free to correct me if I'm wrong.
There are leveraged trading platforms such as kraken and bitfinex. Shorting implkes they are using shuch a platform, otherwise they would just say "sell".
what does that have to interest swaps?
When you use leverage, you are taking out a loan. You must pay interest on that loan. This is a currency swap, not an interest swap.