ZR Trem setting

rolls1392

I have a 2003 S470 with above trem.

Each time I try to detune the guitar(Eb), the bloody trem returns to normal pitch(E).

Is there a way of detuning the guitar and stopping the trem taking up the slack as such.

There is an allen key thing on the back of the guitar but its function is beyond me!!

Thanks in anticipation.