Two representative examples of H II region spectral fitting around auroral lines where our single-region procedure leads to significantly better results than the standard total spectrum fitting. Left column: region 498 in NGC1566. The RMS of residuals around the [NII]λ5756, [SIII]λ6312 and [OII]λλ7320, 7330 auroral lines (from to bottom) is respectively of 283, 719 and 998 when considering single-region fitting, but reaches values of 1462, 1597 and 1611 when considering total spectrum fitting. For this and the other galaxies observed in AO-WFM, we exclude from RMS evaluation around [NII]λ5756 the wavelength region with λ_obs ≳ 5775Å, where the flux is masked because of sodium absorption. Right column: region 513 in galaxy NGC5068. In this case, the RMS of residuals around the [NII]λ5756, [SIII]λ6312 and [OII]λλ7320, 7330 auroral lines is respectively of 329, 241, and 1581 when considering single-region fitting, but reaches values of 1489, 1799, and 1933 when considering total spectrum fitting. The corrected spectral error is represented as a shaded region in the residuals panels.