B.P.M. Match

Sometimes I'm a little bit confused with this option. I listen to loop pressing tap tempo to find current tempo, but when I go to BPM Match option and there is completely different tempo. What is going on? What for is this beat option there? Could someone explain me how to use it properly?

The BPM match option in the 4000 is incredibly reliable. Make sure you have the right amount of measures set ahead of time.

Peace
ian

PS Watch the youtube video I made about the "mpc 4000 and the amen break"

Still cannot get it. It doesn't work as on your video...