MA957 Working Pressure keeps falling

I just set up my Milwaukee MA957 and i set the working pressure on the right gague to about 10psi but it keeps slowly falling back towards zero. Is this normal? Is there a certain way i am suppose to set it? I can constantly see the needle on the right gague tick and fall a little bit... and then it goes back up. I hope it's not damaged.. i loosened the adjustment knob all the way before releasing the cylinder valve just like the instructions said.