I counted 37 floors. If there are 37 apartments per floor since the building looks square-ish (those would be some small apartments) and there are 2 rows (one on each side of the building), that is less than 3k apartments. If each had a family of four, that is less then 12k.
I wouldn't be surprised if the numbers were off by an order of magnitude. 1500 units with on average 2 people works out to 3000. Looking at the pictures, that feels like a more realistic number.
That’s about 50 units per floor. Which does seem a bit low from looking at the pic. But 1000 per floor (to give you the 30k) seems way too high, unless the units are the size of broom closets.