Illustrating how line centroids are shifted towards faster velocities around a 3.0 M_Jup planet, at two azimuths ϕ_p = ±30°. The crosses on the left indicate the location of the line profiles with the same colours on the right. The blue cross is the location of the observed peak perturbation, and the pink cross is the mirror pixel at the other side of the disc. We note that depending on the planet azimuth, the peak perturbation is projected either on the upper or on the lower emitting surface, which contribute differently to the observed line profiles. This contrast leads to variations in the observed line centroids (vertical black lines on the right) and the retrieved velocity fluctuations (in red).