Uncertainty in the derived values for core mass and atmospheric metallicity due to the assumed uncertainty in J₂ for interior models assuming constant envelope-Z. For ΔJ₂ about 10 × the current Juno uncertainty, corresponding to 2 × the estimated error from applying ToF 4 (bottom panel) the core mass uncertainty amounts to ~ 0.04 M_⊕ (middle panel), while the uncertainty in Z_atm is found to be less than 0.0002 (upper panel). These uncertainties are small.