Have you checked the Help file?
Large volume adjustment is for clips, not for tracks. The maximum positive adjustment is +6db. So when you set up the large adjustment to 12db it could be possible that nothing happens.
If you want to increase the clip volume more than 6db, you can use the audio gain option. Right click on the clip and choose audio gain.
NilsW, as I stated in my question, Large Volume adjustment does nothing to clips and has no effect on the clips themselves. I know how to use gain thanks