Projected confidence contours of the SED parameters for the observed system at z = 1.7529 considering the Al ii/Al iii ratio (upper panels), the Si ii/Si iii ratio (middle panel), and the combination of both column density ratios (lower panel). The projections in each of the three possible planes are shown (Δ₁ versus Δ₂, Δ₃ versus Δ₂, and Δ₁ versus Δ₃; from left to right). The outer right panels display the confidence contours considering the enhancement of the break at 3 Ryd, i.e. Δ₁ − Δ₂ versus the strength of the 4 Ryd break Δ₃. The upper and middle panels show the 1σ (marked areas) and 3σ (dotted lines) ranges of confidence. Since there are no SEDs that reproduce the Al ii/Al iii and Si ii/Si iii within  < 3σ simultaneously, the lower panels indicate the regions in parameter space where both column density ratios are matched within 5σ confidence.