If you're wondering what those 5-character sets appearing after many of our titles are, you've come to the right place to get an answer.
They have nothing to do with an available format - but if you're an eBook reader, each one of those sets of digits is a secret discount code that can be used to purchase the eBook it appears under at a 50% discount.
Is there a string attached? Sure. You have to order it at the only place honoring the codes: Smashwords... but don't worry: they offer the book in all of the popular reading formats, so whatever you're reading on, there will be one for you.
To get to the place where you can order the eBook and take advantage of your 50% discount, use the link that's one or two places to the left of the code link you used to get to this page. It says Non-Kindle eBook.
By clicking on that, you will be taken to the Smashwords webpage that offers the book you are interested in, and during the ordering process of that eBook you will be given an opportunity to enter the discount code... so go ahead and take advantage of it.