Inverter node is not inverting.

Hi there blender is giving me hassle again!

Basically I’m doing some compositing and am sending an image of a white blurry area on a black background into an inverter. But it wont invert it, it just turns everything white. Whats up with that? Shouldnt it invert ALL the colours?

Show node setup and attach your blend file

Ok heres an image without the inverter RGB box ticked (i.e. doesnt do anything/original image):

And when the box is ticked:

Obviously, i know an inverter (which on the manual website is described as producing a negative image), should make the background white and the blurriness black, so why isnt it happening. I can upload my blend if for somereason it is required, but dont see why that is necessary. It should just take the HSV’s input and… invert it? XD