Solution : https://service.sap.com/sap/support/notes/569318 (SAP Service marketplace login required)
Key words : 
&sdaccdpc-bldat&su        net amount    output tax      final amount         credit su   &sdaccdpc-wrbtr&&sdaccdpc-wmwst, prerequisites abap dictionary structure sdaccdpc, &=    &sdaccdpc-brbtr&&sdaccdpc-brbtr_off&, &vbdkr-dpnet&su                              tax, &/ su   amount, final billing document, downpayment_value su   clearable, billing document print, sapscript form rvinvoice01, milestone billing document
Related Notes : 
       
| 887703 | Rounding difference in print output of down payment clearing | 
| 626451 | SAPscript: Invoice printout with down payments | 
| 586442 | Down payment request number not available for print | 
| 555279 | Enhancement of billing document printout: Down payments (3) | 
| 532052 | Values for down payments missing in billing docmnt printout | 
| 523803 | Enhancement of billing doc print: Down payments (2) | 
| 304408 | Enhancement of billing document printout: Down payments (1) | 
| 113347 | Down payment process. as of Release 4.0x (standard) |