Adjusting the volume
The vertical slider on the right-hand side of the program's window can be used to adjust the volume during playback (see the screenshot below).
When you move the slider up, volume decreases. When you move the slider down, volume increases.
The number just above the slider indicates the volume percentage. In the above screenshot, the volume percentage is 70%. When the slider is totally 'up' the number indicates 0% (no sound whatsoever). When the slider is totally 'down', the number indicates 100% (maximum volume).