I have gone 10% coupon option.
I'm seeing the notice ("You have bought B1~B3 of S3. We will issue you a 10% value coupon. However, you have the option to give up the coupon and apply a 7.7% refund.") but I'm not seeing how to select one or the other yet. Did you actually select one on the site yet?
Edit: Oops - the notice is clickable - doh. Sorry!