Why am I getting different PD result when I do the experiment twice?

PD results are obtained from the scanned card and the facial features, acquired by the phone's or laptop's camera. 

If you are in a stable environment, results should be very consistant, with very slight deviation. Any of thoses results are approved.

Although most of such parameters are controlled in the algortithm, some marginal deviation between two scans is expected, due to different card holding position or eyes gazing. Deviation could also be observed if the environmentals conditions change.