Solution : https://service.sap.com/sap/support/notes/203814 (SAP Service marketplace login required)
Key words : 
additional key words afs, purchase requisition --> purchase order, form routine j_3a_size_ex, previous partial transfer, source code changed, purchase requisition, purchase order, source code, ekpo-menge, schedule line
Related Notes : 
       
| 198275 | Error msg 305(61) for partial conversion PReq in PO |