There are in fact 4 groups of 45, every time 2 groups will start together, at the end of the qualifiers every competitor will have sailed against each other.

Also see the NoR:
6.2.1. Qualifying Series: The fleet will be split into 4 groups which will be selected by a seeding committee. The 4 groups will form 2 rotating starting groups. Each group will sail a minimum of 6 qualifying races. The qualifying races are scheduled for Monday and Tuesday. If at the end of any day 6 qualifying races have not been completed, the qualifying series will continue the following day.
6.2.2. Final Series: Once the qualifying series is over boats will be split into the Gold Fleet and the Silver Fleet. The top half of the fleet will race in the Gold Fleet and the bottom half of the fleet will race in the Silver Fleet. In the event of an uneven number of boats there will be one extra boat in the Gold Fleet.