I understand that SubCtaDe is the main account in case that you use sub-accounts, for example if you have in any system the accounts:
100000 banks
1000001 bank of america
1000002 wells fargo
1000003 union bank
so in this case the value SubCtaDe for 1000001, 1000002 and 1000003 is 100000
I don't think this applies for SAP systems.
I hope it makes sense.