MSP430F6779A: Calibration; Active Power scaling factor for 1PF is different compared to a 0.5C PF

Part Number:MSP430F6779A

I am using the MSP430F779A and the 'emeter' sample code (although mapped to my hardware configuration).

I am using the GUI to calibrate the meter. I have a set up of;

Voltage = 246V
Current = 24A
PF = 1
Apparent Power = 5.91kW
Active Power = 5.91kW
Reactive = 0kW

I have then calibrated against a reference meter and Active Power scaling factor came out at 2207 and the Phase scaling factor 397.

I then checked the values against a 6uH + 1K load and noticed that I would have to change the Active Power scaling factor to 4553 and change the phase to 253.

So my question is, what should I do to make sure the values are always accurate?