Behavior of Δt (the age derived from spectral fitting minus the age from isochrone fitting) for the subsample of clusters with high-resolution metallicities from the literature. Isochrone ages are from A. P. Milone et al. (2023) supplemented by the compilation in G. Gonçalves et al. (2020, Table 1). The top panel shows Δt as a function of metallicity. The tendency lines are obtained from LOESS. The bottom panel shows the density distribution of Δt. In both panels, the color code identifies the stellar library that was employed in modeling the SSP templates.