We correct the values of the group delay dispersion of the cavity mirrors and N2, as well as the concentration of CO2, obtained from the measurement of the center frequencies of cavity modes using a comb-based Fourier transform spectrometer. The corrected values of group delay dispersion are a factor of 3 higher, which implies that the precision and accuracy of the dispersion measurements is 0.3 fs2 and 3 fs2, respectively.