Estimated envelope rotation rate and number of selected reference models as a function of the threshold in χ_dip². Upper panel: Envelope rotation rate as a function of the threshold value in χ_dip² using the fiducial model as the synthetic observation. The reference models are selected from the M, α_MLT-grid. The input value is shown with the grey line. Threshold values of ρ = 0 and ρ = 0.98 are shown in blue and orange, respectively. Lower panel: Number of models selected as a function of the threshold value in χ_dip². Synthetic observation and stellar model grid are the same as in the upper panel. The colours have the same meaning as in the upper panel.