What does this equation mean?

Define the channel-attributable transfer rate for exposure class c$\in$\{V,H\} as $T_c$=$\frac{\bar I_c-I_0}{1-I_0}$ . This is a direct borrowing from the attributable-risk fraction used in outbreak epidemiology, where it measures what share of disease in an exposed group would disappear if the exposure were removed; here it measures what share of a model’s trait incidence would disappear if its exposure to the source artifact were removed, holding everything else about the model constant. $T_c$=0 means the exposed class shows the trait no more often than baseline: no signal. $T_c$=1 means every trait-negative case in the exposed class would have been positive under full exposure: the strongest possible signal. $T_c$ is dimensionless and bounded in [-1,1] ; a negative value, exposure suppressing the trait relative to baseline, is possible and would itself need explaining.