Top panel: electron fraction profile at t ≈ 30 min past explosion in the inner ejecta of the M_Ch delayed-detonation model 5p0_Z0p014 (dashed line) and the M_WD = 1.06 M_⊙ sub-M_Ch detonation model 1p06_Z2p25e-2 (solid line) shown in Fig. 1. The markers in the upper panel are shown such that the ordinate corresponds to the Y_e of the nucleus (e.g. Y_e = 28/58 ≈ 0.483 for ⁵⁸Ni) and the abscissa to the interpolated velocity on the Y_e profile for the M_Ch delayed-detonation model (both ⁵⁶Ni and ⁶⁴Ni are synthesized in this model but the Y_e profile does not intersect the Y_e value of either isotope). Middle and bottom panels: abundance profiles of stable Ni isotopes for both models. The insets correspond to a logarithmic scale, revealing minor contributions to the total stable Ni abundance from ⁶¹Ni for the M_Ch model and from both ⁶¹Ni and ⁶²Ni for the sub-M_Ch model. No ⁶⁴Ni is produced in this sub-M_Ch model.