[Plugin: DukaPress] Amount of order doesn’t update after updating quantity

Hi All,

I add an product ($20) to cart.
When I checkout, I update quantity of this product to 2 and it show $40 for total.
But the total amount of this order still is $20 when payment.
I try to view information of this order in admin page, total amount still is $20.

Please help me to resolve this issue.
Thanks for your feedback on this in advance!