Yes, 15 alcoholic drinks per person. If you go over, you then pay for them.
One tip--on port days when you are less likely to get to 15, get some unopened beer/cider/seltzers to keep in your fridge to help on those long sea days--you can even order them on the app to be sent to your room.
You could also bring a bottle of wine aboard each to help stretch.
But I'll be honest--DH starts his day early. Only ONCE did we both go over 15 drinks...luckily our friends hadn't so ordered one for us...server knew us well (and we tip a dollar or 2 each order along the way), so was fine with that.