Fractional age (bottom left) and absolute age (bottom right) distribution of the number of stars that are above the 18 M_⊙ track (referred to as N₁₈₊) in Fig. 5. The colored distributions are theoretical predictions for CSF, and two other star formation histories (SFH2 and SFH3) where young stars have a lower probability (top right panel). The gray line indicates the distribution that we derived using observations.