https://userapps.support.sap.com/sap/support/knowledge/en/3482095
3482095 - Sales Orders with 'Not Performed' Overall Credit Status are also displayed in VKM4 | SAP...
Sales order that are not relevant for credit check and the credit status is 'Not Performed' are being displayed in the report from transaction VKM4.
https://userapps.support.sap.com/sap/support/knowledge/en/3521320
3521320 - The select results are different while executing the t-code VKM4 | SAP Knowledge Base...
Selection results differ when running transaction VKM4 with the Credit Control Area set to blank (empty) compared with '*'.