I think a lot is being lost in the translation here. I mean, Verily's analysis is a laboratory *determined* COVID-19 incidence rate in the sewersheds right? How is it any different from the laboratory *confirmed* incidence rate they compare to? As far as proportional, I think you are right. When laboratory confirmed goes up, both Verily concentrations also go up. When laboratory confirmed goes down, both Verily concentrations also go down. I doubt there is a constant scale factor operating here unless the laboratory confirmed is using a similar method of normalization (i.e., they all start with copies per gram dry weight).