I am not getting correct value for Watts when i did the calculation, example as below

Actual reading from meter = 232.20 Volts , 2.89 Amps, 665.00 Watts, 1311707.00 KWH

232.20 x 2.89 = 671.06 Watts, but in the meter it shows 665.00, can i know why its not accurate ?

Thanks in advance.