QTR-Quadtone RIP

Yes, this can be confusing at times. I found the easiest way to get a grip on this is to play around, create some fake curves and look at the graph you get after pressing "show curve". Some trial and error gives already quite some insight.

Having said that, QTR assumes the "gray" inks to form the backbone of the inks: a series of grays in different densities. The darkest "gray" is black and starts at full black; the others blend in at smaller densities. The "toners" are supposed to influence the tone. Depending on the inkset they are true color pigments (C&LC, M&LM in the OEM inksets) or gray inks with a different tone then the "grays". This is the case dedicated B&W sets (such as UT14). In those B&W sets, the practical difference between the terms "grays" and the "toners" becomes blurry. They become more of a label than a real difference. 

Hope this helps 

Joost