Results of the linear least-squares fit to refine the period spacing value. Upper panel: linear least-squares fit applied to a subset of 14 periods of NGC 246 (see text for details). The resulting period spacing is ΔΠ = 12.902 ± 0.045 s. Lower panel: residuals of the period distribution relative to the dipole mean period spacing. A thin orange line connects modes with consecutive radial order.