Discrepancies, defined by Eq. (6), as a function of fixed temperature contrast (T_star ± 300) and with the filling factor (f_het) varied from 0.01 to 0.15. Positive errors (R-TLSE overestimation) dominate for cool spots, while negative errors (R-TLSE underestimation) arise for hot faculae. Extreme cases (e.g., f_het = 0.15, ΔT = ±300 K) show maximal divergence. The dashed lines delineate boundaries at −50, −20, −10, 10, 20, and 50 ppm.