Left panels: distribution of χ² as a function of the flux of Al III (top) and total C IV profile (bottom). Black continuous lines mark the normal distribution associated with simulations. Gray horizontal lines indicate the value at and at . The gray vertical line indicates the mean of the normal distribution. Middle panels: spectra of the quasar SDSSJ222753.07-092951.7 in the 1900 Å blend (top) and total C IV1549 (bottom) spectral ranges. Gray shadow regions correspond to the models at the confidence level obtained from the Monte Carlo simulations. The blue line corresponds to the SPECFIT result. Right panels show the distributions of the fluxes of Al III (top) and total C IV (bottom) for all the models under the 1σ confidence level plotted in the left panels. Vertical lines has the same meaning as in left panels.