In this case you’d lose $500 per coin, which means $1,500 in total.
Now imagine you’re bullish on ether and its price is currently at $4,000. You take a long position on 3 coins. You close the position when the price drops to $3,500. As your prediction was incorrect, you’d incur a loss. In this case you’d lose $500 per coin, which means $1,500 in total.