Solution : https://service.sap.com/sap/support/notes/29896 (SAP Service marketplace login required)
Key words : 
field            ga quantity      mcvbap    zmeng        mcvbap     zz_gameng            ga, sd customizing => reporting => sales info system 1, zz_gameng - credit memo request quantity corresponds, customizing logistics controlling => data collection 1, additional key words credit memo, standard sap system information structures, credit memo request key figures, product  salesdoc  item   update group, mcvbap    netwr        mcvbap     zz_gawert 2, zz_gawert - credit memo request
Related Notes : 
       
| 204130 | SIS update: Collective note | 
| 174141 | SIS: Collective note - Customizing |