Solution : https://service.sap.com/sap/support/notes/1180789 (SAP Service marketplace login required)
Key words : 
rm system writes, customized img entries, define template character '-', num format characteristics, running key figures, write negative values, write negative, key figure, primary output, _val characteristic
Related Notes : 
       
| 1167498 | RMGMT210: Corrections in Support Package 13 |