The evolutionary stage and the surface A(Li) of HE 0057-5959 . Left panel: position of target star HE 0057-5959 in the Hertzsprung-Russell diagram (red square) in comparison with the theoretical track of a star with 0.76 M_⊙, [Fe/H]=−1.0 dex and [α/Fe]=+0.4 dex, coloured according to the predicted A(Li). The colour-scale is shown on the right side. The model is re-scaled in order to match the average A(Li)_nlte of the RGB stars by Mucciarelli et al. (2022). Right panel: A(Li)_NLTE as function of log(L/L_⊙) for HE 0057-5959 (red square) in comparison with the RGB star sample by Mucciarelli et al. (2022, cyan circles) and the stars of the metal-poor ([Fe/H]~−2.0 dex) globular cluster NGC 6397 (Lind et al. 2009, grey circles). The luminosity level of the RGBb for the metallicity of HE 0057-5959 is marked with an arrow.