SLX rear shifter – indicator problem

I have just fitted a new SLX rear shifter and cannot quite understand what is causing the indicator to play up. Its on a reverse action dereileur and going from the smallest on the cassette indicates:
full right gears 9 to 3 inclusive
half way on gear 2
full left on gear 9

Its not indicating correctly, but it does move – so it must be connected. Is it duff and in need of sending back or is there something easy I can do to fix it?