hi @FXHochban
Its tooltip is right and wrong. If the value is positive it returns negative. if the value is negative it returns positive. Therefore inverse (reversed signs).
The changing of rotation on 1 axis can alter the resulting forwards axis (or any)because of something called Gimbal Lock, which appears like a kind of axis flip. Therefore depending how far you rotate 1 axis it can flip one of the others ie. Z becomes X.
Euler rotations confuse many using unreal or any other animation package.