Spectra of J1538+0855 (grey), showing our best-fit model for each epoch (red). The grey bands represent the regions masked during the continuum and emission lines’ fit. We fitted a power law (blue) to the spectrum and Gaussian functions for the emission lines (green curves). The best-fit power law derived following the method of RH20 is shown as a solid magenta line, along with points R₁ (median flux of points with rest-frame wavelengths between 1701 and 1725 Å), R₂ (1677–1701 Å), R₃ (1280–1284 Å), and R₄ (1415–1430 Å) being used to define and anchor the power-law slope. The green triangle was used as reference for the continuum level since the R₄ point falls within the red end of the SiIV emission line.