From my Blue days, it was exactly at published departure time minus 24 hours [cue much tapping of the F5 key, and it turns up on the dot!].

Be there at 1300 [or whenever] at T-7 days.

Brownies are allowed to book on the Upper Deck at T-7, I believe. Your only problem will be that Gold and Silver will usually have got there first [] and the bassinets seats are still T-72 hours.