At the end of March Sony shipped a total number of 22.3 million PS4s worldwide. Now that Vgchartz started updating numbers again after 6 weeks they have the PS4 at 21.4m total sales. Is it reasonable to think that at that time 900k weren't sold? 

With only 3 additional days from where the numbers of the month are not yet counted and a part probably somewhere in the distribution chain I think the PS4 is undertracked, again. 

NO. NO. NO. NO. NO. NO. NO. NO.
Is also overtracked, confirmed by Sony, by end of February VGC have PS4 at 20.34 million when Sony say 20.2 million.

/Thread.

900k on shelves is very reasonable. An overtrack is more likely than an undertrack.

It is possible.

Hell no, 900k is pretty low if you ask me

That's why I'm asking? What is then a reasonable amount that is on shelves?

Overtracked... I think thats the word you were looking for.

900K in the retail channel is the least I would expect for PS4, the rate it seems to be selling. I would expect over 1 million in the retail channels. But in terms of VGC accuracy 900K vs 1 million or 1.1 million left on shelves is doing OK.

The nitpick level of this thread it off the charts.

More than a million on the shelves is not so strange and it is literally also not on shelves some were at that time on their way to shops/warehouses.