Hi Mike,
IDOC:
GROUP -> RemoveContext -> Sort -> SplitByValue (Value Change) -> collapseContext -> SplitByValue (Each Value) -> IDOC
No need to do mapping for IDOC field since this is already 1..1. As a rule, in the mapping editor, when you see it is green it means that there is no need to map it 
Problem I'm facing now is for the mapping of BEGIN and HEADER field.
Just map BEGIN with a constant (value should be 1), the HEADER field can be mapped with an empty constant.
Regards,
Mark