RCM Data processing in SNAP

Hello, I am processing Radarsat Constellation Mission (RCM) data with SNAP. I only have the covariance matrix (do not have the scattering matrix). I did sigma naught radiometric calibration of covariance matrix in SNAP. It is confusing for me what do we get after generating sigma naught of covariance matrix. I could not find any equations they have used in SNAP. Do anyone have idea about this? Thank you in advance.