I wouldn't be surprised if it came much earlier than 20 days though. Mine came 7 days (4 working days) after I took the exam, and I know other people's came even earlier than that.
Don't get too hung up about it though. If it's been three weeks and you still haven't gotten your score then I would call them, but there's not a particular day when you can expect it. Middle 80% of people probably get it between 4 and 10 days after the exam.
Good to know. 20 days would be a long time to wait to see the official score.