Value mapping in AIF AX2012

Hi.

Creating the danish OIOXML electronic invoice document via AIF in AX2012. In the XML file the unit is specified as “Stk”, I want to change this to the value “EA”. How do you setup this value mapping in AIF. Thought it was to set up the value in Value mapping on the outbound port for the document - but this does not give me “EA” in the file. So if anybody knows - please…