can input offset be negative for single supply mosfets ?

Hello All,

I have implemented  current measurment using shunt and LMC6482A in differential mode. I have supply voltage from 12 V.  some how the measured out put value of the Opamp is far less then calculated value. At 0.5 amps current through a shunt of 2 mOhm, and differential amplifier gain of 133.45 I expect op amp out put of 133.45 mV. But I am measuring around 64mV.  I checked out data sheet of LMC6482A, 1.35mv of input offset is menctiond. I am bit surprised. I would like to know whetherthi offset could alo be negative draging my measurmen!!

Thanks & Regards,

Krishna