Questions about Course Statistics

Can someone explain the course statistics numbers for me? This example doesn’t seem to add up.

Screenshot 2024-02-28 at 18-44-20 LingQ Learning Languages Simply

Particularly, why are there only 919 unique words, but over 2,000 new words? Is it counting each new word multiple times? But then the New Words + LingQs + Known words don’t add up to the 20,000 total words.

Am I missing something, or is there something off with these numbers?