Field help (SFIGRUFLG) 

This flag is used to specify if the source documents are grouped on the same target document, with respect to the the value of the invoicing element.

Yes

The documents are always grouped.

No if different

Two source documents having a different value on an invoicing element are not grouped.

SEEINFO Only the value 'Yes' can be picked for invoicing elements in amounts.

SEEINFOIf a return contains deliveries with a different rate for an invoicing element set up with the value 'No if different', then return lines cannot be grouped on a single credit memo.This only applies to invoicing elements expressed in percentage.