Did you open the valve all the way open and got the full pressure? Or did you just crack it open and try to get the guage to read about 10psi and could not get it down to the 10psi range?A couple people including me had a nice encounter with this "flow control valve" at the beginning of last year. It turned out that this thing isn't lowering the pressure of the gas as a real regulator does. You get full 800+psi on output. A flow rate is impossible to keep stable.
I'm still surprised to see the device for sale. I guess the safety guidelines of the CGA (Compressed Gas Association) do not apply to consumer goods.
Keep your hands away !