What is profit/loss?
Profit/Loss is the total "paper" (or unrealized) profit or loss for all open positions. Note that for long positions you have a paper profit (loss) if your opening cost is lower (higher) than current valuation. For short positions you have a paper profit (loss) if your opening cost is higher (lower) than current valuation. The unrealized profit or loss does not affect your currency balances until the positions are closed.
Suppose you have two short positions open. One has an opening cost of $3,000 and a current value of $2,500. This position has a paper profit of $500. The other has an opening cost of $2,000 and a current value of $2,100. This position has a paper loss of $100. Your total profit on the two positions is $400.