Δν − ΔΠ₁ diagram of the core-helium burning stars used in this work. The seismic estimate of the stellar mass is color coded. The low branch corresponds to stars ascending the RGB. Most of the outliers below the global trend of the RGB were identified as stars with a mass transfer by Deheuvels et al. (2022). Typical uncertainties are below 0.1 μHz for Δν and below 4 s (1 s) for ΔΠ₁ for, respectively, RC (RGB) stars.