Is this a sound bug?

I have a scene that is 37.2 seconds long. I use a loop that is 8 seconds long and repeated 5 times.

In the sound editor, I step the sound down to zero level at exactly 37.2 seconds.

What I expect to happen is that the sound and movie end together, in reality, however, the sound stops before the movie.

I am using a frame rate of 25 ps and I think I get about 4 or 5 frames more AFTER the music has stopped

What’s happing ???