Discount amount at checkout

I’ve noticed while doing some test orders that once you are in the checkout process the box to the right will show this:

Price Quantity Discount Subtotal

$684.00 1 $17.61 $615.60

I’m giving a 10% discount which would be 68.40, the store is calculating the Subtotal correctly but is obviously showing the incorrect Discount amount of 17.61.

Is there a bug or fix for this?

This works properly for me.

Are you using a catalog or cart promotion? What are the conditions and bonus for your promotion? Also, double check that no other promotions are being applied - this could interfere with your desired promotion.