Using Receipt Number field (Alias: CKNU)as an additonal information column while entering JEs using

Hello All, I am looking at the reasons as to why Receipt Number field (Alias: CKNU) can't be used as an additonal information column while entering JEs using P0911? In our existing data, it is either populated as R09801 for some RB batches. For some other K, M or RB batches, either batch or document number is populated. What would be the implications in terms of data entry or reporting if "Receipt Number field (Alias: CKNU)" is used while entering journals using P0911? Thanks in advance for your help.