The adopted model of the upper RGB LF (5) for different values of its free parameters. The top left panel shows a reference model (black solid line) with (a, b, c, m₀^TRGB, σ_TRGB) = (0.1, 0.3, 0.4, 14.5, 0.1) alongside the nominal value of the tip magnitude m₀^TRGB (vertical dashed line). The other panels show how the model changes when changing a single parameter while keeping the others to the values of the reference model.