To make CDS, you instill the chlorine dioxide gas into water. That gives it a measuring capacity. If you have a 3000 ppm/L of chlorine dioxide (that's what you need the testing strips for to find out what your ppm/L is), and you use 1mL of CDS, you have the equivalent of 3 drops of regular activated MMS.
Jim Humble has a YouTube on JimHumbleLive dated 2/9/2012 revised, as I recall, and he will show you how to make CDS "the old way" (which is actually the way I make it, because I make it in volume, but not in the volume someone who retails it would make) -- that will give you a clearer picture of how it is made, using a heat source for the MMS/CA mixture.
We've since played around on the forum here with several other ways to make CDS (it's always about combining MMS and CA and siphoning off the chlorine dioxide gas into water, regardless) -