Dipole (ℓ = 1) average of the computed period spacings, , evaluated in a range of periods that embraces the periods observed in GD 358, shown as curves of different colors for different stellar masses. We consider a mean effective temperature for the star, T_eff = 24 469 ± 1018 K, resulting from averaging T_eff = 24 000 ± 500 K (Koester et al. 2014) and T_eff = 24 937 ± 1018 K (Bédard et al. 2017). We adopted the mean period spacing ΔΠ = 39.25 ± 0.17 s derived in Sect. 5.1. We include the error bars associated with the uncertainties in and T_eff. The stellar mass derived by interpolation is M_⋆ = 0.588 ± 0.024 M_⊙.