price: Optional price or price distance for selling the position, or 0 for selling at market. A positive price or price distance constitutes an exit stop, a negative price is an exit limit (similar to Entry). An exit stop closes the position when the asset price is at or worse than the given price, like a stop loss; an exit limit closes the position when the asset price is at or better than the given price, like a profit target.
It is a little vague, but it seems that the value is relative to market price. This interpretation is consistent because price=0 means exit at market.
