In the Audio Settings tab in the VLC Preferences, the Always reset audio start level to option always takes the current volume level in VLC, so if you had set a default volume of, say, 100%, if you open the Preferences window while at a 47% volume and save any changes, the default volume will now be 47%.
Even if that's the intended behavior, there's still something else. Try to open the Audio Settings while at a 200% volume. You'll get something like this:
So the slider looks wrong. Not to mention the tooltip says you can set a value from 0 to 1024.