(Left panel) The best-fit curve of growth obtained from the equivalent width values measured in the Day 7 spectrum of V1369 Cen. Na I D lines are located in the flat region of the curve of growth, suggesting that they are saturated and hardly usable for precise abundance estimates (see also Fig. A.1). On the other hand, Ki and Li I lines are located in the linear region. This allowed us to estimate the lithium over-abundance and infer the amount of lithium mass in the nova ejecta from the Li I 670.8 nm absorption line. (Right panel) The posterior distribution for the Doppler parameter b and the column densities N_i derived from the MCMC procedure applied to the curve of growth best fit.