Evolution of k₂ as a function of the hydrogen mass fraction X_c inside the star for three GENEC models with an initial mass of 32.8 M_⊙, overshooting parameter 0.20, Z = 0.015, and ξ = 1; the single version with initial rotational velocity v_eq,ini = 100 km s⁻¹ (blue); the single version with zero initial rotational velocity (v_eq,ini = 0 km s⁻¹, violet); and the single version with zero initial rotational velocity to which the empirical correction for k₂ of Claret (1999) has not been applied (red).