Fractional difference between the number of detected galaxies in the simulations, n_sim, and in the observations, n_obs, as a function of the i-band magnitude cut. Red scatter points refer to the GALSBI-SPS model, while blue box plots to the phenomenological version in Fischbacher et al. (2025a). The GALSBI-SPS error bars consider Poisson noise on the counts, while GALSBI box plots have been constructed using the posterior samples in Fischbacher et al. (2025a). The dashed black line marks the perfect agreement in the number counts with observations.