ADX / iADX returning different doubles...?

Hi,

Placing the standard ADX indictaor that ships with MetaTrader on a chart and checking the Main Signal against an indicator that maps the Main Signal returned from iADX (using the same parameters as the one shipped with Metatrader) that is also placed on the same chart will give two different values. Does anyone know why?

Regards,
lucidlamp