The derived P-L relation, where the colour represents the fraction of power in the power spectra, derived from the FFT of the radial velocity, on the stellar surface for each identified mode in the models. Data points for 0.7 and 0.8 M_⊙ models are faded to emphasise the 1 M_⊙ models. The lines with different patterns correspond to the linear fundamental and first-, second-, and third-overtone periods (P₀, P₁, P₂ and P₃, respectively) interpolated from Trabucchi et al. (2019). The non-linear fundamental period and its maximum limit (respectively P₀ NL and ${\mathrm{P}}_0^{max}$ NL) follows the analytical formulae derived from Trabucchi et al. (2021).