Histogram containing the differences between the inferred and the input atmosphere at selected optical depths for the region enclosed by the orange square in Fig. 1. The differences in temperature, LOS velocity, magnetic field strength, and inclination are shown from left to right. Each row corresponds, from top to bottom, to reference layers at log τ₅₀₀ = [0, −1, −2]. The bin size is 10 K, 0.1 km s⁻¹, 10 G, and 2 degrees, respectively.