Models from scenario B for different values of the clump absorption coefficient τ_C and differentforeground screen depths: τ₀ = 3 (black), 3.5 (blue), 4 (red). The variation of τ_C has theeffect of expanding the dynamic range covered by the model. The variation of τ₀ shifts the curve to higher extinction values. For τ₀ = 4 the model is traced for 20 (black), 5 (red), and 2 (green) clumps with τ_C = 0.5 each. Models overlap on the plot and, in fact, all start from the same value. The 20-clump model is the one which covers the whole dynamics. The models reproduce the fact that increasing the number of clumps on the line of sight has the effect of enhancing both the flux and the extinction as observed.