Solution : https://service.sap.com/sap/support/notes/137543 (SAP Service marketplace login required)
Key words : 
global settings --> check units, additional key words mf50, repetitive manufacturing planning table, rounding logic applies, planning table, transaction mf50, system displays, 0 decimal places, longer displays, prerequisites release 3
Related Notes : 
       
| 140837 | MF50: Rounding for entry or processing | 
| 115871 | MF50: Rounding error |