Effects of different choices of outer disk radius, R_out, for the ray-tracing on the emergent disk spectrum. The relative error is calculated as $\frac{F_{R_{\mathrm{out}}}-F_{2000R_g}}{F_{2000R_g}}$. F_r denotes the X–ray flux calculated with R_out = r. We use F_2000Rg as the reference spectrum, as regions beyond 2000 R_g do not produce significant X–ray emissions due to the disk temperature decreasing as a function of radius. In the last test (bottom–middle), the values of the disk parameters are similar to our best-fit results for AT2018cow (Table B.4).