Comparison of the mock observations and the spectra from the two retrieval approaches. The mock observation is shown in black. The median spectrum from the posterior derived using the fast and full approach are shown in orange (shifted up by 1 Jy) and blue (shifted up by 0.5 Jy), respectively. While the upper panel shows the full wavelength range of the mock observation, the middle panel shows a zoom-in to the line-rich region around 6.5µm. The lower panel displays the residual (defined as ((F_obs – F_mode1)/F_obs) in percent between the two retrievals and the mock observation, with the coloured areas indicating the 1σ uncertainty of the retrieved fluxes.