Let's see
Goods price £6,000- 10% deposit of £600 paid via credit card, let's assume the rate was £0.85, so would show on the card as €705. £6,000 (in total) at that time would have been €7,058.
So, euro rate is now £0.95, so when you pay the £5,400, it would show on your card as €5,684. In...