Residuals between the observed and modeled normalized fluxes as a function of the wavelength for the 17 324 RVS spectra in the testing set. The color represents the residuals, and the spectra are sorted by spectral S/N, increasing from bottom to top. S/N = 22, 50, and 100 is indicated by the dashed black, blue, and red lines, respectively. The Ca II line within the DIB window is marked as a dashed green line.