Distribution of the continuum levels for 750 different synthetic spectra (see Sect. 2.2) determined with the methods: (A) maximum, (B) mean, (C) mean considering the bins around the maximum of the spectral histogram, (D) median, (E) median of the selected bins, (F) the 25th percentile, (G) the 75th percentile, (H) Gaussian fit, (I) Gaussian fit to the selected bins, (J) the maximum of the KDE, (K) the sigma-clipping method, and (L) the corrected version of the sigma-clipping method as introduced in Sect. 2.4. For each panel, we indicate in the top-right corner the mean, median and standard deviation of the distributions (see also Table 2).