IMU (Razor-9DOF)

Hello;
I am using 9DOF razor IMU from sparkfun.
I could find the code for GUI Python and sample code for uploading on the micro controller (on the IMU board), atmega328 from sparkfun website. the code is: "IMU_Razor9DOF.py" and "SF9DOF_AHRS.pde". I change one part of the code on "SF9DOF_AHRS.pde "to see the Euler angle instead of the raw data.
My problem is whenever I run the GUI python code the reference direction of IMU is changes. I couldn't find how can I change the reference value to zero for each axis. for example if I take the board parallel to the ground the Pitch and Roll value become zero. But in my experiment it is not like this even every time in the random direction.
there is a video in youtube which help to understand my statement. (I cannot add it now, since I am new in this forum), search for IMU Razor 9 DOF in youtube.

I appreciate any help or hint. Please let me know if my question isn't clear.

Thanks;
SB