Contour plot of Δχ² values for each of the host-galaxy dust (A_V) and GRB redshift (z) parameters used in the fitting grid (Sect. 3.1) in comparison to the best-fit power law (β = 0.9) and SMC-like dust model. The other dust model contour plots are not included, as they do not portray any different information. The inset is the broadband SED, the black dots are GROND data, and the blue line depicts the best-fit power law. The significance levels for 3 d.o.f. are: 1σ = 68.3%, Δχ² = 3.5, 2σ = 90%, Δχ² = 6.3, 3σ = 99%, Δχ² = 11.4, 4σ = 99.99%, and Δχ² = 21.1.