Hadn't noticed, but I see it now. Usually this indicates an amenity floor (like we'll see in the Marriott Renaissance) or mechanical floor (notably Place de Ville C), but I don't think either of those are true in the case of the 17th floor of the Azure Westboro.One thing I've noticed about this tower that the 17th floor is taller than all the other floors. Seems to be reflected in the new render if you look close and I've never seen other towers designed that way.