Absorbed line ratios of Mg XII/O VIII over Mg XI/O VIII (left panel) and Ne X/O VIII over Ne IX/O VIII for N_H = 0.20 × 10²² cm⁻² and the resp- ective observed line ratios for BD +30 (error cross). The symbols have the same meaning as in Fig. 8 (or Fig. 9). The parallel lines indicate the shift of the crossed models (and the “best-fit” model as well) if the original bubble abundances of Mg (left panel) or Ne (right panel) are multiplied by the given factor. The corresponding shifts of the remaining bubble models are not shown in order to avoid confusion.