Store Credit Doesn't Deduct - Amazon.

So I'm using the NEW Amazon Login and Pay extension with OC 2.0.2.0 all set up and working fine, but the store credit doesn't deduct when authorizing the payment.

I am talking about the store credit that you can place on customer transactions.

So if I have £10 credit and purchase £9.99 worth of goods I would still be charged £9.99.

any help would greatly be appreciated, Thanks Liam