After careful measurement with the inner graduated cylinder, I can confirm that the markings are 2.02g per 0.01".
So, if I want to report my CoCoRaHS the way the gauge would read, I divide the total mass of water collected by 202.22. If I want to report more accurately, if the funnel was on I divide the total mass of water collected by 213.458, and if the funnel was off I divide by 216.879.
Today's rain is 3.07" by direct reading, and 2.90" by correcting for more accurate funnel area. If I had collected that rain in the main tube without the funnel on it would have been 2.86". That amount of variation seems significant to me.