FIF application to the indices available in the LEGA-C ID 209466 galaxy spectrum. The vertical dashed brown lines indicate the feature boundaries for each index, while the grey shaded regions represent the pseudo-continua used for normalisation. In the upper subplots, the black lines and blue shaded regions correspond to the observed spectrum and its associated uncertainty, respectively. The solid red line represents the best-fit derived from the posterior distribution. The green lines in the lower subplots show the residuals between the observed spectrum and the best fit, with the yellow shaded region indicating the relative uncertainties of the observed spectrum.