Welcome to cruising. This is how it is done on all mainline cruise lines.
I always leave more than the suggested minimum
This is the breakdown listed on Carnival.com
For your convenience, we automatically charge the gratuities for dining and stateroom staff to your onboard Sail & Sign account. The total amount is $10.00 per guest, per day (our recommended guideline) as follows:
$ 3.50 Per Day Stateroom Services
$ 5.50 Per Day Dining Room Services
$ 1.00 Per Day Alternative Services: distributed to other kitchen and hotel service staff