Accelerometer data... What to expect?

Hi,

I have started working with the MPU-6000. I am reading sensor data registers (ACCEL_XOUT etc.). registers. After converting the register value to g-values I have noticed that I get a maximum g value of approx. 500mg (0.5g) if I hold the board in such a way that earths gravity is parallel to the axis I am measuring (x,y or z axis). What I am trying to say is that I am applying 1g and I am reading 0.5g. I want to know the following:

+ Is this normal behavior of the IC?
+ Do I need to calibrate my device to get the right g value? In that case how should I do it?

Thank you very much for your attention.
Cheers