Can't subtract area with weight tool (character rigging). What's wrong ?

[recipe-union]

I'm trying to remove some areas on a hand model with the Weight Tool in subtract mode, but nothing is happening. What am I doing wrong here ?! Please see attached C4D file.

Hand3.c4d

[Dr. Sassi]

Hi recipe-union.

Thanks for the file!

I can reduce it by subtracting it from the point shown in your picture.

My best guess is one or the other might lead to a problem:

1
If the point selected has no joint selected that carries anything that allows for subtraction (Wrist or index), nothing will happen.
2
Perhaps your intuition tells you to move the slider to the left, which feels subtractive and natural. But the slider needs to get to the right, as the value chosen must be positive. Otherwise, you have a double "negative".

Sorry, guessing might portray your question as if you didn't know what to do, which is not my intention. I can only assume, otherwise, I would just say, do this or that.

I hope all of that makes sense

Cheers