Variation in χ² as a function of different values of the inner radius of the disc from 6 to 200 R_g using MODEL 3 (top panel) and MODEL 2 (bottom panel). The highlighted boxes in the figures show the best-fit value of the inner disc radius for the two models (R_in = 15 ± 3 R_g and R_g), and the error bars associated with each χ² value represent Δχ² = 2.7, corresponding to the 90% confidence level for a single parameter.