When you finish a heads up challenge with someone, you take all the points and they get nothing. However, this affects the cards and it changes them to show final results of points instead of how many each person got during the actual matches so its hard to actually compare. The percentage of correct answers does not compare accurately so I believe it would be better if the “points earned” reflected what each user actually got while completing the challenge, while on top it would show how much you took away from it at the end.
In co-op, it lists the percentage of the total you got right, which if you got everything right is 50%. I believe it would be better if the percentage was of how many you did, and at the top they can be added for your combined right out of total.