Panel (a): Schematic representation of the sdB star’s interior structures for the logarithm of the diffusion coefficient of mixing during the core He-burning stage, using convective penetration combined with the CPM scheme. Different levels of mixing are indicated by the grayscale bar on the right-hand y-axis. The hatched area represents semi-convection in the transitional zone between the convective (gray) and radiative (white) regions. The figure shows four points with varied ages (A = 20, B = 60, C = 100, and D = 127 million years). Panel (b): Period spacing of KIC 10001893 (blue) and the period spacings of the four models depicted in panel (a) (red). The order of the panels corresponds to their ages, with the youngest at the top and the oldest at the bottom.