Relative residuals, multiplied by 1000, between the observed and asymptotic mixed-mode frequencies in KIC 6144777. The color of the symbols indicates the azimuthal order: dark blue squares for m = −1, light blue diamonds for m = 0, or purple triangles for m = 1; 1-σ uncertainties are also shown. The dashed line corresponds to a perfect fit. The dotted lines show the frequency resolution plus an extra-modulation Δν(1 − ζ)/100, which is empirically used to define the quality of the fit.