Location of DB WDs on the T_eff − log g diagram (Kepler et al. 2019), marked with small black circles. Also depicted is the location of the published DBV stars (gray circles), according to the compilation by Córsico et al. (2019). The target star of the present paper, GD 358, is highlighted with large red circles according to spectroscopy; the two locations of this star correspond to two spectroscopic determinations of T_eff and log g according to Koester et al. (2014) (T_eff = 24 000 ± 500 K, log g = 7.80 ± 0.05), which are very close to the recent derivations by Kong & Luo (2021), and according to Bédard et al. (2017) (T_eff = 24 937 ± 1018 K, log g = 7.92 ± 0.05). The location of the asteroseismological model (see Sect. 5.2) is emphasized with a blue circle. The DB WD evolutionary tracks of Althaus et al. (2009) are displayed with different colors according to the stellar-mass values (in solar units). The blue-dashed line represents the theoretical dipole (ℓ = 1) blue edge of the DBV instability strip, according to Córsico et al. (2009).