I'm sorry for the confusion. This isn't an error, the issue is that the discount doesn't show up until you move to the next page.
NOTE: Print + ebook bundles are shown as two separate items in your cart. Discount and bundle pricing will be shown on the order summary page.
When you hit Proceed to Checkout, you should see the discount.
Let us know if you have any other questions.
O'Reilly Media, Inc.