I got the same offer and booked 7 nights out of Baltimore. I'm traveling solo, so all I paid was $196.00 for taxes, port fees, and gratuities. The fine print on the mailing says its "valid for two sailings". I booked it directly on the Carnival website. And the website is allowing me to make another reservation for another free cabin. I just need to decide where to go on my next free Carnival cruise.