Relative difference of the Bessel gravitational moment solutions J₂ (top) and J₈ (bottom) compared to the ToF solutions. Results are shown for different numbers N of used spheroids. We compare our implementation (This work) to the one used in Movshovitz & Fortney (2022) (M&F 22) for different orders of the ToF. We also show the influence of using cubic spline interpolation with the parameter n_x that stands for the number of points that were calculated without interpolation.