ΔⁱG P-value indicates the P-value of the observed solvation free energy gain. The P-value measures the probability of getting a lower than observed ΔⁱG, when the interface atoms are picked randomly from the protein surface, such as to amount to the observed interface area. The P-value is a measure of interface specificity, showing how surprising, in energy terms, the interface is.

For example, P=0.5 means that the interface is not "surprising" at all with ΔⁱG equal to an average value for given structures. P>0.5 means that the interface is less hydrophobic then it could be, therefore the interface is likely to be an artefact of crystal packing. P<0.5 indicates interfaces with surprising (higher than would-be-average for given structures) hydrophobicity, implying that the interface surface can be interaction-specific. The limiting case of P=0 means that no other interface of the observed area may have a lower ΔⁱG, therefore such interface is a truly unique spot on the protein surface.