In a 4/4 time signature, the number 4 above the line indicates that there are four beats per measure, and the note that usually gets the beat is the quarter note.
In a 4/4 time signature, the number 4 on top indicates that there are four beats in each measure, while the number 4 on the bottom indicates that a quarter note receives one beat. Therefore, the quarter note gets the beat in 4/4 time.
