It is important to note that while atomic spin plays a role, it is the spin at the s-orbitals (ρ s s ) that primarily contributes to contact shifts due to their radial probability at the nuclear position |φ (0)| 2 . Generally, Fig. suggests a correlation between ρ s and ρ s s . A linear correlation between contact coupling A FC K with ρ s s is expected, with the slope equated to the hyperfine coupling constant G for an unpaired electron in the atomic valence s-orbital (ns). Fig. confirms this correlation well for H atoms, with the slope close to the observed hyperfine coupling constant for the H 1s electron (G = 1420 MHz). However, this correlation does not hold for C atoms as shown in Fig. with the 2s electron (reported G = 3760 MHz and we calculated 5520 MHz from ZORA-PBE0 method), indicating the radial expansions of atomic s-orbitals are significantly altered due to different bonding interactions of valence 2s and 2p orbitals, leading to varying polarization effects on the inner 1s orbitals. Furthermore, deviations of the slope from the atomic values are more pronounced for EPR-III compared to IGLO-III in Fig. , suggesting greater perturbations to the atomic orbitals with EPR-III, leading to poorer performance as shown in Fig. . These analyses of atomic spin populations and their correlation with calculated Fermi-contact hyperfine coupling constants provide valuable insights into the effectiveness of different DFT methods in predicting contact shifts.