Observed (blue) and synthetic (orange) spectra for Arcturus. Vertical green and orange dashed lines identify spectral lines differing by between 3 and 5% and by more than 5% in relative flux, respectively. These spectra were computed adopting the final GSP-Spec line list and are shown at the RVS spectral resolution with 800 wlp. We note that the wavelengths are shown in vacuum. Some line identifications are shown for non-blended absorption lines with a normalised flux below 0.93. The lower yellow insets show the difference between the observed and synthetic fluxes.