Values of log χ² for the input frequencies of the t1-asp-3freq exercise are represented with a colour map (see legend in the figure for the related scale) in the M − R plane of the grid of models. The chemical composition and overshooting (X, Z, α_ov) are those of the χ² global minimum in the top panel and those of the input model t1 in the bottom panel. A cross symbol is located at the real position of the t1 model.