Dependence of S/N on the G-band magnitude. Dots color coded by T_eff show our final 6594 solar twins, while gray dots represent 27 782 stars without imposing the condition on the seventh digit of the GSP-Spec Quality Flags on parameterization uncertainties. Red thick curve shows the cubic polynomial relation between the G-band magnitude and the common logarithm of S/N, obtained by fitting the gray data points.