Precision of the HOTPAYNE label estimates as a function of T_eff. Plotted are the differences (residuals) between the labels from HOTPAYNE and the true values for a test set of Kurucz model spectra with S/N ~ 100, color-coded by the true values. The numbers marked in the figure are the dispersion derived from a Gaussian fit to the residuals. The precision of the HOTPAYNE label determination varies with T_eff and [X/H]. For metal-poor stars of [X/H] < −1 dex, the [X/H] estimates may suffer large uncertainties. However, we note that in the real case of the LAMOST survey, we do not expect there to be many hot stars with such low metallicities.