CMYK adjust - strange behavior

Help
1

CMYK adjust has a strange behavior.
All sliders have an initial position of 0.000
When I increase the slider of Reds, the color intensity of Red becomes weaker. The same with Yellows. Minus values increase intensity.
For Greens and Blues it is the other way around.

Is this a bug or does this behavior make sense?

2

The whole area of color wheels needs attention, and IIRC the devs are already on it because a bug report for this exists for quite some time. You may want to search it in bugs.kde.org

3

But hopefully not all color filters will be faulty. What tools do you use to enhance colors, alos just for color correction?