For 30 cc green plus 30cc blue: green will block 50% each of the red and blue light, passing 100% of green light. Applied to this light is a blue filter which will block 50% each of the red and green light, passing 100% of blue light. The combined result is: red = 50% x 50% = 25%, green = 100% x 50% = 50%, and blue = 50% x 100% = 50%. So the relative color result is the same as the previous example, where green and blue light have equal strength, and the red light is 1/2 of that strength. However, in this case, all of the actual light transmission percentages are only 1/2 of the previous example, consequently we have to double the exposure time.
Ahhh, I didn't think of that. Thank you, Mr. Bill.

But, Mr. Bill, I STILL do not understand why, if a print is "too cyan" in hue, you would "correct it" by adding more cyan AT ALL whether that be with the use of a cyan filter or rather with a combination of blue and green filters? With either method, it appears you are still adding proportionately more cyan than red to a print that the artist has already deemed to be "too cyan."

I know that in your industry you do not handle red filters. Pardon my asking, but why this complication at all? It seems unnecessary given that you could just devise a red filter and be done with it. I don't mean to sound irreverent of a craft, which I, on the contrary, respect very much. But as an admitted layperson to photography, this decision not to use red filters sounds completely arbitrary and self-handicapping.

Thank you, Mr. Bill.