Solution : https://service.sap.com/sap/support/notes/87009 (SAP Service marketplace login required)
Key words : 
symptom transaction mrhr     program sapmm08rwhen entering, purchase order gr item, additional key words jva, mm integration manager   20c_hp4, program change, quantity invoiced, quantity receipted, error g4027, rounding problem, prerequisites solution
Related Notes : 
       
| 95939 | Goods Receipt GR with Invoice Adjustment | 
| 93554 | @3Z@ 4. collective oil fixes/transports after HP34 |