Touchpad scroll direction to change volume is reversed

[Stuart Langridge]

When using a laptop touchpad to scroll on the sound indicator, the scroll direction is reversed; scrolling up decreases the volume, and scrolling down increases it. I understand that for actually _scrolling_ a document or similar, "natural scrolling" makes sense (one is moving the "document" underneath the "glass", similar to how scrolling on a touchscreen works), but that's not the case when explicitly setting the volume; there is no document being moved there, and scrolling "up" makes more sense to set the volume "up", not "down". (I suspect that this is because there is a global setting to implement natural scrolling by reversing the meaning of "up" and "down" in touchpad scrolling, and this global setting is being incorrectly applied even to things that shouldn't have natural scrolling such as volume setting in the sound indicator.)