Solution : https://service.sap.com/sap/support/notes/305596 (SAP Service marketplace login required)
Key words : 
additional key words rohps, variable-size items, production order, entry quantity, resb-erfmg, requirements quantity, program error, relative notes, source code, correspond
Related Notes : 
       
| 145511 | Requirement qty not rounded for variable-size item | 
| 110734 | CO01: Requirement quantity of a size not rounded | 
| 108300 | Incor.size quantities after change i. qty i. header | 
| 98901 | Unit size number not in EA without decimal places | 
| 93874 | Incorrect requirement quantity f.variable-size item | 
| 73033 | Component quantity in production orders |