Not 100% sure but I think it’s open by 7am. I would not worry about being late, ticket reservations are wide open starting May 1 for both one park and hoppers.
You will be at DL the same week as I am. I have the same message, even though I did a room only reservation at Disneyland Hotel. I think it's just a heads up when the dates will be available to do park reservations. Probably also covers them for people who think they are done when they buy a package, that they have tickets, but not reservations yet.
I just went through this process for the first week of July. Your tickets have to be on your Disney account page (linked) the window opens at 6am PST each day. I am in Colorado so it was 7am Mountain time.