Position in the HRD of all the N23 sample stars in different metallicity bins (we use their ‘Corrected-Literature’ value for T_eff ). Grey symbols correspond to stars on the subgiant branch (SGB) and to the peculiar objects (legend in the insert). Li abundance (3D,NLTE) is colour-coded for the 57 ‘normal’ (colour-coded) Plateau dwarf stars (indicated as MS in the insert) that we use for the comparison with the theoretical Li predictions. Solid lines show the MS part of the computed evolutionary tracks computed for the middle [Fe/H] values of each bin except for the upper left bin that shows models at [Fe/H] = −5.8 dex that we computed assuming the C and Na content of the most Fe-poor dwarf, J0023+0307, for which we also show the error bars on its luminosity.