Hi,
Have you created a value field w/r to the field EXTI1 in CO-PA? If yes, then you have to create derivation strategy using t.code. KEDE as mentioned below:
1. Select Vlookup options
2. Then input the table name
3. After that in source field select the field name and in target filed maintain the CO-PA value field and save it.
If you want further clarification refer below link:
Derivation Types - Profitability Analysis (COPA) - SAP Library
Regards,
Mukthar