The SFT-10 SCF pump operates in a mode that once the CO2 tank regulator is opened, CO2 liquid will flow through the pump and equilibrate into the sample vessel to tank pressure (typically 750 psi given the vapor pressure of CO2 is ~750 psi at room temperature). CO2 is in reality a liquid-gas and compressible at lower pressures. What you will observe once you have started pumping CO2 into your sample vessel is that from tank pressure up to about 1250 psi, the pressure increase is very slow because you are pumping liquid CO2 that is rather compressible. Once you have crossed over the 1250 psi range, the density of the liquid CO2 has now approached 1 gram/ml and the liquid CO2 begins to pump very similar to any traditional HPLC type pumping unit.
Further complicating this answer is the fact that it is always assumed that the sample vessel has been filled with raw materials of varying densities and the dead volume within the sample vessel varies from experiment to experiment based on how well the raw materials were packed into the sample vessel. All of the above variables influence the actual “fill time” of your sample vessel in a traditional SFE experiment.