have you read the online companion The Lexington Letter?
https://books.apple.com/us/book/severance/id1613220757
it's free download on Apple Books, it's a side story written by the creators of the show. Gives some insight or suspicion into what the job entails/what they're really doing, etc. Worth reading 100 percent.
includes a 22-page Macrodata Refiner's orientation booklet.