Edited September 21, 2018
at 11:03 AMby
This seems to be for relatively new authors. Not sure if any of these will be good but, I didn't see this anywhere, but from the text on the page:
"To claim your $3 eBook credit, please sign in or create an account.
Credit must be used on an eBook on the deal page.
Credit must be claimed and used by 11:59 PM PDT September 30, 2018.
You can read your eBook on Kindle e-reader or Fire tablet, or any device with the free Kindle App."