Because the credit score is really a ‘ how safely milkable are you’ score it counterintuitively benefits you to keep a balance on the card that isn’t over some threshold. You can sign up for their free credit score monitoring service and observe where that balance lies for each service somewhere around 40-60% but don’t quote me in that.
Too high of a balance and you’ll lower your score. Carry a mild balance and increase your score. Pay that balance off and take a small hit.