AD8422 amplification issue

We are using op-amp (P/N: AD8422BRZ) to measure current using Rsense (10 ohms resistor). The calculations and simulations are matching but the actual measurement doesn’t.

 For the given below circuit, With 270 ohms load, I = 86mA.

Drop across R50 = 860mV.

 Which means 430mV should be across +IN and -IN pins but we measured 414mV. This 16mV error is acceptable.

As per transfer function.,

Vo= (1+ 19.6K/Rg)*Vdiff + Vref

     = (1+19.6/15)*Vdiff + 1

     = (2.32*0.414) + 1 = 1.96V

The simulation also shows same 1.96V as like calculations. But measured value in our board @ TP6 is 2.9V. Please let us know what is been missing at our end..