This may sound cruel:
There are so many restrictions it is fairly worthless. Book a guarantee in the category you are happy with and hope for the best.
Notice the categories it doesn't include. Most of those are guarantee categories, suites and lowest category. It isn't a deal for singles and isn't available on 1/3 of their fleet.
If you REALLY are interested call your agent and ask them if you qualify and the answer will probably be no or you will have to give up the cabin you now have and take a chance with an "iffy" upgrade.
It's good to look at the offers and I applaud you for noticing the fine print but the "Devil is in the details".