The first round was 19 1-minute math problems, I forgot to submit it fast and my multiple correct answers didn't get in. Then I got straight rejection. I am confident in my math level, and I think they just have a very weird interview process.
First round was a hard online assessment, very fast paced quick maths. Then a few interview rounds over zoom. Fun questions! Mostly probability, but more about intuition and general problem solving.
30 minutes, many questions on probability / stats, of the type you get in the green book. You get around 45 seconds to answer the questions which is very hard. Interviewer is nice though.