True, should have said 250 1080p movies on one terabyte...
Basically, since a 1080p movie is around 8GB in size, then the 4K version will be roughly 36GB.
So divide 250 by around 4 to get the number of 4K movies and you have around 60 4K movies on one terabyte.
With the added terabyte capacity of around 400 terabytes, there's additional room for over 20,000 4K movies.
That's a lot.