I am reading data through I2C. The calculations performed are correct (Converting high and low bytes into a 12 bit value and using 195mg/digit to convert data into scales of +/- 400g level.).
There is a noise of about +/-10g in all the three axis. So the graph will always be fluctuating when the device is kept still.
Neglecting the +/- 10g noise, the X and Y axis data are fine. But Z axis data is always shifted by about 8g. So the Z axis data has an average of 8g, when the device is upright and kept still, which had to be 1g. So the graph of Z axis will be fluctuating at 8g with.