Solution : https://service.sap.com/sap/support/notes/110734 (SAP Service marketplace login required)
Key words : 
additional key words co01, production order, system displays, component quantity, size rounded, source code, release smaller, implement note 73033, solution repair, prerequisites
Related Notes : 
       
| 305596 | Size: BDMNG does not correspond to ERFMG in order | 
| 108300 | Incor.size quantities after change i. qty i. header | 
| 79149 | Alternative UoM: Incorrect adjustment of comp. qties | 
| 73033 | Component quantity in production orders |