Assuming that they have 5M ready to go , and that each plane can handle 150k units, that's thirty planes or so... I would think that they wouldn't really want to ship them all at the same time for a laugh, they have been probably been shipping 2-3 planes daily I would think... So for the past two weeks or so. It is hard to imagine that taking 2-3 planes would have a major impact on the entire fleet.
It's probably closer to 500M units, because in every major country around the world, every business will want 1 for every employee, every school will want 1 for every student, and every citizen wants 1 for their own personal use.
So they've had to buy out the cargo space for 500m / 150k = 3,333 planes from China in the last week.