It might also account only for permanent residents as opposed to refugees/refugee claimants/ temporary immigrants (such as seasonal workers, or in general workers without a permanent status, temporary visitors, international students etc).

I imagine most Ukrainians in Poland don't have a permanent status. Though i might be wrong.

There is so much more in the book than in the movies. The movies focus on the romance but most of them miss the subtle satire that is to me one of the best parts of Austen's books.