In the FX market you don’t invest a particular sum on a trade. For 1 micro lot (1000 units), a pip value is about $0.10
So as the market keeps moving against you or in your favour, you keep losing more or making more until your Stop Loss order or Take profit order (if you had those) are triggered. Every pip would cost you about $0.10
The broker however takes part of your balance as margin for each trade, which is returned when the trade is closed whether you win or lose.