This offer is for those with a Kindle with Special Offers only. View the Special Offers on your Kindle (Menu, Special Offers) and you should see a new promotion (if you don't, turn on your wireless, click Menu, Sync & Check for New Items, then after the sync has completed, go to the Special Offers screen):
Save $10 on a $25 purchase of select software downloads at Amazon.com
Click on offer, then click on the link on the offer page sign up and get an email with the promotion code. Sign-up for this offer expires on September 17. You'll get an email (right away), a link to list of eligible downloads and a promotion code to enter at checkout. Once you have the promotional code, you have until October 17 to complete your purchase. Like previous offers, this one requires you to use the full checkout process in order to enter your promotional code. Also, like all Amazon sales that use promotional codes, if you have a gift card balance, you must use it for the payment (if there is not a sufficient balance, then you can pick which credit card or other payment to use).
This offer is limited to one per device AND one per customer (and, like all recent offers, is non-transferable).
There is a very limited selection and I only found two below $30 and a handful under $40 (although there are a number of items in the hundreds of dollars range). If you were already going to get one of these choices - perhaps updating your financial or antivirus package, then it's a $10 gift, but otherwise it isn't much of a discount on most of the items.