The answers are likely already here on NLG.
First, just below your post is a very recent thread on getting a manual.
"I have some manuals for the VLC machines and some working knowledge of some issues.
Call me at 1(306)961-8456
email is:
bradwilliams@sasktel.net
Willing to share what you need no charge..
Brad Williams"
Next there's a manual (you have access to) in the NLG File system for a VLC 8724. I'm not up on these machines but here's a screenshot of the volume control adjustment on that machine. It may be similar to yours.