Evolution of nebular mass fractions vs. time for the 0.625 M_⊙ sequence from Fig. 24 with Z = Z_GD. Shown are the total (ionised) mass enclosed by the outer nebular boundary, M_ion(R_out), with the different contributions of the shell (light grey) and rim (dark grey) indicated. The different lines indicate mass fractions contained within certain distances R from the star for which the real gas velocities reach distinct limits:  contains all mass shells with (thick dashed line), and  is the corresponding mass value for [O iii] 5007 Å (thick solid line). HWHM refers to the total, volume integrated line profile. The thin lines (solid and dashed) indicate the masses enclosed by the radii R_HW10%M where the (real) gas velocity v corresponds to the half width of the 10% intensity level of the integrated line profile, i.e. v = V_HW10%M.