Vapour pressure of a liquid subjected to pressure
Here's how it works.  The fugacity of the liquid at temperature T and total pressure P is equal to the equilibrium vapor pressure at T times the Poynting correction (assuming that the vapor phase behaves as an ideal gas mixture).  The fugacity of the same species in the vapor is equal to the partial pressure of the substance in the gas phase.  The vapor and liquid are at equilibrium at temperature T and total pressure P if the fugacity of the substance in the liquid is equal to the fugacity of the substance in the vapor phase.