If the market had gone the other way and GBP/USD had fallen by 20 pips, you would have lost $200, less than 1% of what you paid for the currency pair.
Or you could have opened your trade with a leveraged provider, who might have a margin requirement of 10% on GBP/USD.
Here, you’d only have to pay 10% of your $128,600 exposure, or $12,860, to open the position.
If GBP/USD rose to 20 pips, you would still make the same profit of $200, but at a considerably reduced cost.
Of course, if GBP/USD fell 20 pips then you would still lose $200, too – a larger loss in comparison to your initial deposit.