FIELD_START_BYTE is a field used throughout the application.

!Distribution Segments
It may be used to define the starting position of the segment. It does not count ‘-’ or ‘.’ as a position i.e. Distribution code: 1234-56-789

Segment 1 starts at position 1 Segment 2 starts at position 5 Segment 3 starts at position 7 

!Interface File
The field may also be used to define the start position within an interface file. This is used if the File Format is a 'Fixed Format'. The Beginning and Ending positions must be continuous without gap.