You're comparing apples to oranges here. The 11.7M as of March 31 was worldwide shipped (aka sell-in). The 13.4M as of now is sell-through to customers, and only in JP/NA/EU. So the total worldwide shipped now is quite a bit more than 13.4M.
Until you can provide those added numbers we can only go with what Nintendo has given for example the numbers in Japan from Nintendo themselves show digital sales are lower than what people thought it would be in the the region.