Solution : https://service.sap.com/sap/support/notes/328142 (SAP Service marketplace login required)
Key words : 
support packages sapkh31i63, emu participating currency, -emu participating currency, currency translation reason, terms subsequent settlement, subsequent settlement, local currency, reference currency, variances occur, agency business
Related Notes : 
       
| 398739 | Incorrect conversion of EMU currencies - Part 2 | 
| 183379 | Composite SAP note subsequent settlement (Purchasing) 4.6 | 
| 152725 | Collective note: Subsequent settlement (Purch.) Release 4.5 | 
| 123298 | Euro: Conversion of document currency in sales&distribution | 
| 104668 | Collective note: Subsequent settlement (Purch.) Release 4.0 | 
| 40147 | Collective note: Subsequent settlement (Purch.) Release 3.0 |