I think it's "pay for 5 and get 6" but I could be mistaken. We've gone through 3 of them on a cruise because Skyline is our favorite bar. We go there before and after dinner typically. The Dream does have a Skyline bar, but I don't remember if they have the passport.
Edit: It's pay for 6, get 7. To get your money's worth, get the more expensive ones with the passport. We pick the ones that have glow cubes in them.