Playback sound duration with Speaker

[mforbiz]

Hi.

I've created a multisim circuit to study an LM386 Audio Amplifier :

If I set the Playback Duration i.e. to 10 secs, I need to run the circuit for much more than 10 secs to obtain a playback sound of 10 secs.

I dont' understand why.

Any idea?

Thanks in advance