After adding fields on KNA1 using append structure, not null dn't work

Question

Hello, all.
let me ask you something.
after adding fields on standard table 'KNA1' using append structure, not null , default value doesn't work.
when I check table using data object check(utilities > data object > check),  the report says like this.
Fld name  Position Data Type     Length Decimals Not null  Default
MANDT    1            VARCHAR2 9                           X           '000'
KUNNR    2            VARCHAR2 30                         X            ' '
LAND1    3            VARCHAR2 9                           X            ' '
ZMBRN   178        VARCHAR2 30                          X            ' '
ZKUNNR 179        VARCHAR2 30      
ZSEQ     180         VARCHAR2 12      
fields ZKUNNR, ZSEQ  doesn't check not null, default.
Any advice will help.
thank in advance.

Answer 1

Using 'initial values' check at SE11, I can explicitly make a filed not null.
but when I use append structure, there is no way for checking 'initial values' check at SE11.
thanks anyway.