Solution : https://service.sap.com/sap/support/notes/1239139 (SAP Service marketplace login required)
Key words : 
terms nriv snro tnro offldocno itl_ofdnum reason, buffering type main memory buffering, number range group itl_ofdnum, number range object beabilldoc, feature official document numbering, number range buffering, range group beabilldoc, official document number, complete document numbering, identifying primary number
Related Notes : 
       
| 1294779 | SAP CRM 5.2 - SP07 | 
| 1294778 | SAP CRM 2005 - SP Stack 14 | 
| 630914 | Regenerating individual objects in a BE application | 
| 599157 | Number ranges: new buffering method | 
| 504875 | Buffering number ranges | 
| 453979 | Performance CRM Billing - composite SAP note |