Amazon: Select Discover Cardholders: Add Discover Card, Make Purchase $20.01+ get $20 Off YMMV

I was trying to add discover card and found the below offer in my account.
Step 1
Add your Discover Card to Amazon
Click here to add your Discover card to Amazon without getting your card out.
Step 2
Use your Promotional Code at Checkout
Select eligible products worth $20.01 or more, sold and shipped by Amazon.com. Then enter your promotional code at checkout: DISCOVERPD
Step 3
Pay with Discover
Check out with your newly added Discover card.
$20 off will reflect on the final order page if the items are eligible for the promotion.
https://www.amazon.com/b?node=20547486011