Comparison between absorption spectra with and without the correction for the spot velocity, illustrated for the Na I D₁ line and for two different v sin i values. Top: averaged absorption spectra in each case. In green and cyan is the POLD shifted by the spot-induced velocity. In dashed red and pink is the POLD computed using only the Keplerian velocity of the planet. Bottom panel: relative difference contribution of the spot for each of the cases.