Not magic Spotti
I think I read something that Maersk in the beginning understated the capacity in order to make sure such big ships would work and could really carry that. If I remember right, when under construction the e-class was given with 13.000 TEU. If that is correct, then the later increases are not that "magic", however unusual for sure, but easy to do by just increasing the
container tiers on deck. And "behind" the accommodation (bridge), virtually, the sky is the limit !!
I sailed not that big container vessels, mainly in the 2500 TEU range, but jacking up the
TEU capacity is rather easy. In front of the bridge we could on those vessels take 7 high
instead of 6 and so on to the forward. Therefore, another layer (tier) empties on top und
presto,,there you have another 250 or so TEU more. It is of course only a theoretical number.
the max capacity with mixed container, but all full, was about 65% of theoretical TEU.
At that point the max stability/draft was reached. Usually, rough said, hatches all full
2 full tiers on deck and about another tier, the 3rd at about 50-75% full. At that time most container ships are full .Of course,,there is then plenty space above free, but that is gone
because the vessel reaches the max stability capacity and can not load any more by that criteria,
but is way off from it,s given max TEU capacity.
I personal think ,this bigger number that better is only for "news creating", nothing really to do
with real possiblities of the ships.
brgds
capt ted