Morning Leighton - the way I read this is
from water line to deck = 750 mm or approx 30"
from the deck to bottom of bulkhead doorways = 150 mm or approx 6"
and yes, the draft must be calculated from the the water line to the lowest
point of the hull but only in a vertical plane,
so if you planned some 18" draft the minimium moulded depth of hull would be
18" + 30" = 48" or 1220 mm which for the SofW would be near amidships
Derek