Full posterior distribution for the three main stellar population parameters measured during the second step, namely total metallicity, [Mg/Fe], and IMF slope Γ, for the observed spectrum shown in Fig. 6. The green solid lines indicate the median of the distribution, while dashed vertical lines mark the 16th and 84th percentiles. Our fitting approach is able to capture and successfully break the degeneracies of the inversion problem even when fitting stellar populations characterized by an extended SFH.