How is it that we know these numbers of illegals?
Because the IRS gives out Taxpayer Identification Numbers TINs like candy. As long as the taxes are withheld and remitted they are perfectly happy with illegals working illegally.
Because they know how many they shipped there
Haha! Good question.
It’s like when the media makes claims that they couldn’t possibly know, they’ll talk about the numbers of things that you can’t possibly measure - like when people come ILLEGALLY, you don’t know how many there are. Or how many brought drugs. Or how many were raped. Or....
...but they’ll claim to know, it’s astonishing!

My guess is the way they arrived at that number is just NY's population share of that 11 million: 11m/330m for total U.S., breaks down to 670k/20m, the population of NY.