Solution : https://service.sap.com/sap/support/notes/1622605 (SAP Service marketplace login required)
Key words : 
prerequisites user system details data, user system details tab, choose existing assignments button, add existing roles/systems, added roles/systems, adding existing assignments, terms access control 2010, existing assignments, access request, symptom create
Related Notes : 
       
| 1607067 | Master Note for SAP Access Control 10.0 - Support Pack 6 |