using a trackpad on a Macbook or a mouse with a mouse wheel to control volume, the direction of control is reversed from what I would expect. Two-finger scroll or mousewheel down increases volume, scrolling up decreases.
Not sure if this is related to the trackpad “natural” scrolling direction change introduced in macOS 10.x or not, but likely. I’m using my systems without “natural” scrolling enabled.
(I’ll test this in Windows to confirm if it’s mac-specific)