Sampled BP (left) and RP (right) spectra are shown in the top panels for source Gaia DR3 6210089815971933056 (G ≈ 11.5 mag and G_BP − G_RP ≈ 1.0 mag). Each panel contains two curves: a blue curve showing the non-truncated spectrum using all 55 coefficients, and a red curve showing the truncated spectrum. The number of coefficients used for each spectrum is given in the label within the plot. The bottom panels show the truncation assessment. This is run independently for BP and RP. The black circles indicate the coefficients normalised by their formal errors, and the red line shows the standard deviation of the M normalised coefficients, starting from M = 3 on the right-hand side. The blue shaded region is the cone given by .