Goodness-of-fit score for each model in the realistic composition at six years based on the [O I], [O II], and [O III] lines. Lower scores indicate a better fit to the data (from Eq. (12), a perfect fit has a score of 0, all three lines off by a factor of two has a score of 0.27, and all three lines off by a factor of ten has a score of 3). The black circles indicate the two models with the lowest scores for each T_PWN, although T_PWN = 10⁵ K has no models with scores <3, and T_PWN = 3 × 10⁵ K has no models with scores <2. The best-fitting models for T_PWN = 10⁶ K are plotted in Fig. 13