Kumon students will be able to get 669 faster than the average non-Kumon student simply due to a large amount of practice though. Students don't memorizate of all the possible combinations, but imo that practice helps tune the mind to be sharp in that particular direction. very useful in some jobs.

it is to be noted that math isn't numeracy though. I have dyscalclia which hurt me with numbers but at the college level there are fewer numbers and more conceptual thinking. ended up with a math minor, though that's due to the CS degree requiring so many classes.