According to
DCL's official
Fun Onboard Q&A page:
<DL><DD>
Is there a romantic restaurant just for adults?
The ship features an adults-only alternative restaurant called Palo. Dining hours
for Palo are 6 - 11 p.m. Reservations are required, and taken (once on board)
on a first-come first-served basis. Palo dining is limited to Guests 18 and older.
There is a service charge of $5 per Guest for gratuities.</DD></DL>
So, for a couple, that's an automatic $10 tip.
Now, suppose you order a $34 bottle of wine. That's another automatic $5 tip (@ 15%). So now we're at $15.
Then, there's blank line on the receipt where you have an opportunity to increase the tip. If the service you get is a good as the service we got, chances are you'll gladly increase the tip by another $5 or $10 to bring the total up to $20 or $25.
It all goes on the KTTW card, and becomes part of the shocking total that you see at the end of the cruise.