Look at the 35th screen of that, it shows exactly where I am
"If you have opened the WAD file you can then create a sounds.txt that will contain only those sounds used in the wad file"
As I understand this fragment: creating sounds.txt from the wad, therefore Sounds.txt currently irrelevant.
But that's the moment when the values reset - and indeed, they reset to those from default sounds.txt.
To me it looks like the program still refers to sounds.txt when it shouldn't do it at all...