LastVersion=10012013000, run in wine.
NL saves config to NeoLemmix147Settings.ini, which I shall call "the file".
I set SoundVolume=24 in the file, play a level and exit the game, then the file says SoundVolume=52.
I set SoundVolume=100 in the file, played a level, sound was louder than last time, exited the game, and again SoundVolume=52 is written in the file.
-- Simon