The ReFH 2.3 Model uses Cmax to calculate antecedent conditions for an observed event in DAYMOD. For more details, see the technical guide here.
In the ReFH2 software version 3.0, the parameter initial conditions were calculated using the catchment descriptor Cmax, and were not updated if Cmax was changed by the user.
Versions 3.1 and above, however, maintain the dependencies between the DAYMOD internal variables (Cmax, FC, RD) when default values are changed by the user.
Download the latest version of ReFH 2 here.