When running KEU5, balancing error (error message: GLT2201) occurred.

Dears,

When running KEU5,

Balancing field "Segment" in line item 000 not filled (error message: GLT2201) occurred. I have checked note 2221237. Because segment is a mandatory field for our project, so it must be assigned. And characteristic 'product' (ARTNR) is defined as a receiver field, according to the note, it is expected to be obtained via derivation in CO-PA. But I cannot figure out what's the meaning of this. Is it mean I need to set something in KEDR? Can somebody tell me the detail of this setting? Thanks a lot.