When you send marketing emails (non-operational), unsubscribe text and links are appended to the bottom. You can change the defaults, here. Here's how:.
Edit the Unsubscribe Message
Under Admin, click on Email.
Edit the Unsubscribe HTML and Unsubscribe Text versions to your liking and click Save.
There you have it. Make sure to test! You don't want your marketing emails to have broken unsubscribe links.