In P6, PV is the 'Planned Value Cost' column, also know as BCWS. And:
"Planned Value Cost is the Budget at Completion * Schedule % Complete. The Schedule % Complete specifies how much of the activity's baseline duration has been completed so far. Budget at Completion is computed from the baseline. When an activity has assignments, the Planned Value Cost is calculated as the Budget At Completion * (Data date of current project - baseline Assignment start date)/(baseline Assignment start date) for each of the assignments and then summed to the activity level."