Solution : https://service.sap.com/sap/support/notes/216810 (SAP Service marketplace login required)
Key words : 
customizing sales document types, sales information system, symptom key figures, delivery-relevant item, prerequisites contracts differ, typical service contracts, delivery-related billing, order-related billing, sales order type, default billing type
Related Notes : 
       
| 1597096 | FAQ: Statistics update in Sales Information System | 
| 813196 | Incorrect contract update | 
| 204130 | SIS update: Collective note | 
| 170183 | |
| 81485 | Open delivery value for rejected contracts |