OC 2.0.1.1 Coupon code problem

Anyone noticed, the coupon code sometimes knocks off more than it should?

This normally reduces by £10, but on this occasion £24 - could it be because the customer has been switching currencies? ove gbp by default and use/eur is also active with same settings as default install.


£80.00
Sub-Total: £80.00
Coupon (tenner): £-24.00
Total: £56.00