Hard to say without knowing the arrangements in place, but what I mean is 'shipped' (which this may or may not be) is not a very useful indicator of success early on because it's effectively a guess at how well a game is going to do. Those units could all be sold (to customers) on day one or most of them could still be unsold a month later, which would be two very different levels of success in reality.
Because even if we assume for sake of argument that is true for sell-through, it can be a significantly lower % if we are only considering the first 24 hours and including all physical copies shipped to retailers.
eg.
900k digital sales
600k physical shipped (100k of those sold in 24h)
Would get you to a 1.5m shipped announcement, and meet the 90% digital (sell through) rule we have arbitrarily applied, but would only be 1m sold-through in 24h.
This would be a meaningfully different performance level to eg.
1350k digital sales
150k physical sold through