We are about to sail on our first princess cruise and I’m confused about dining. We have a group of 9. I tried to book main dining & the only time available for all of us was 8:20, which is way late for us. I called princess, and they booked 8:20 and said we can actually show up anytime- it doesn’t have to be at 8:20- since we have main dining reservations. Is this truly how it works? Seems strange…