When you make an international payment, the money is debited from your account on a real-time basis. However, at the backend (between banks) the settlement can take up to 10 days.
Ideally, the merchant should send the settlement on the same day at the same foreign exchange rate, but if there’s any delay from them, then the exchange rate of the settlement day can be higher or lower than the rate of exchange when you made the payment.
If the new rate is more, then the difference gets debited (gets deducted) from your account.
If the new rate is lesser, then the difference gets credited (comes to you) to your account.
This is called “Fx Adjustment” and can show up on the transactions page.