Hi Liben,
I cannot remember what Hasan said, but I think if your client would like a Number Parent values instead of Alpha Parent values, then if for example, Assets range from 1000 to 9999, I would make AA (All Assets) Parent value to be 1000.
Similarly, if Liability accounts range from 2000 to 2999, then I would make AL (All Liabilities) Parent value to be 2000.

And so for...

Logically, I wouldn't use 9999 for a Parent value.
I hope this helps!
Gavrobere