The 28 data element stores the control number for the functional
group in the Functional Group Header (GS)
and Trailer (GE).
The control number must match for the header and trailer in one
functional group. When Framework EDI, creates the functional
group, the control number is determined by the incremental count of
functional group in the transaction set. This is the default
value and may not be correct for the organization, so it should by
overwritten where applicable.
