Colour Banding Module Issue

I dont think the colour banding module is working for me how it’s supposed to. It’s really buggy. The numbers I add to the threshold of the colour seem to bear no relation to the actual size of the colour bands, plus im getting this weird white box around my original drawing but mainly i just get dots around the outside of the drawing.

In the screenshot which is rather low-resolution, I’m not able to read the text
but from what I do see, the banding module does appear to be working correctly.

What is the effect you are going after? What do you want the lines to look like?