Distribution with respect to mass of the specific AM, j_r, at different burning stages. Shown are the specific AM midway through the MS, X_c = 0.35, at the depletion of hydrogen, helium, carbon, and finally oxygen in the core. Models shown are AN100 (top left), AM100 (top right), TS100 (bottom left), and MTS100 (bottom right). We show a greyed-out area that highlights the inner region up to mass coordinate M₄ as defined in Eq. (36) and listed in Table 3.