This may occur if you or your opponent accidentally reverse the Final Score upon entry. Please be careful to enter your score in the box indicated for your Xbox Gamertag or PSN ID.
You have the ability to edit the Final Score you entered by clicking on the "Edit" button on the "EDIT" button next to your score on the Game Page.
Rival will display an auto-detected score for many games. It is rarely incorrect, but if it is, you may enter your score manually.
Please remember to always take a picture of your games final score screen in case you need to file a challenge to the score.