Hi Huseyin,
I agree with Achim. The performance of your circuit will not only be dependent on the amplifier itself but also to its external components. What is your application circuit and why do you need such precision?
For the offset voltage of the AD8237, it actually varies parts by parts but the typical value is 25 uV. Some of the parts may be below or exceed the typical value but it is guaranteed that the offset voltage of this parts will not be greater than to 75 uV.
The things that you need to consider on defining the voltage across your reference pin will be your input voltage, Gain and the output voltage range of the amplifier. For the inamp, output voltage is equal to Vo = Vin*Gain + Vref. Make sure that your minimum and maximum input voltage multiplied by your gain is always within the output voltage range of the amplifier.
Best regards,
Emman
