No problems.You only start to owe accrue interest when a statement is issued to you for it e.g.
overseas transaction 15 Apr
overseas merchant posts to its bank [unknown]
overseas bank posts to BoC 15 May
(assuming your statement date is 28 of each month)
overseas transaction billed 28 May
overseas transaction payment due:~23 Jun
Only after ~23 Jun will the transaction accrue interest.
If your friend has already repaid the overseas transaction amount now,then the money will sit in the account until offset by the transaction on posting date.If in excess,no interest will accrue.
