Eight bars means eight bars. The time of the beat is not fixed, but the duration of the beat is relative, such as: 12BPM=.5 seconds, a beat is calculated with 6÷12=.5;

a beat of 15 BPM = .4 seconds is calculated with 6÷15=.4, and a beat of 16BPM=.375 seconds is calculated with 6÷16=.375.

Extended materials

In music, time is divided into equal basic units, and each unit is called a "beat" or a beat. The duration of a beat is expressed by the duration of a note.

the duration of a beat can be a quarter note (that is, taking a quarter note as a beat), a quarter note (taking a quarter note as a beat) or an eighth note (taking an eighth note as a beat).