A bond has two interest numbers and they're not the same.
The coupon rate is fixed at issuance. It says "this bond pays X% of par every year." That number never changes for the life of the bond.
The yield is the return an investor actually earns at today's market price. If the bond trades at 98.5% of par with a 4% coupon, the investor is paying less than par but still gets the full 4% coupon — so the yield is higher than 4%. If the bond trades at 102% of par, the yield is lower than 4%.
When the ticker page shows both, the coupon is the contractual number and the yield is the market-implied one. Both matter; reading only one of them misses half the story.