keithley 2400 - CALIBRATION

[Fbra]

Please,

What is this???

When I apply a sorce of 0 V in a circuit, my instrument measure a voltage value different of zero, but approximately of this.

Is it normal? Has it a way to zero my instrument? how can I do it?

Thank  you!

[PeterChang]

How about "AutoZero" ? 

1).Press "MENU"

2). Select "A/D CTRL", press "ENTER". 
3). Select "AUTOZERO", press "ENTER".