Specific entropy differences in the adiabat Δs^presc ≡ s_RHD − s_presc between values provided by the CIFIST grid (Ludwig et al. 2009), and values predicted by the M13 prescription, Eq. (2). Left column: original coefficients from Magic et al. (2013) are used. Here, entropy from the CIFIST grid has been corrected by an offset of 0.04794 × 10⁹ erg g⁻¹ K⁻¹ corresponding to the entropy difference between the solar atmosphere models in the CIFIST and STAGGER grids. Right column: same as left column but the coefficients involved in the M13 mathematical form have been re-calibrated with the CIFIST entropies. Rows: each row displays the models with a given metallicity: [Fe/H] = +0.0 (row 1), −1.0 (row 2) and −2.0 (row 3).