Because it returns the number of files matched. lets do some counting, shall we?

tidy boys - bits and pieces.mp3 -1
tidy boys - chainsaw.mp3 - 2
tidy boys - cant top it.mp3 - 3
tidy boys - colours.mp3 - 4
tidy boys - devotion.mp3 - 5
tidy boys vs tidy girls - blow ya load.mp3 - 6
tidy boys - dance 2 the house.mp3 - 7

7, 7 matched files. I don't see why that is so hard to grasp.