Value Table and Value Range

Hello,

For some of cases Value Range is assigned as either single value or Value table for a Domain.

Lets say If you look at the Table VBFA For the field Data element-VBTYP_N Domain-VBTYP - Document Category

There are fixed value i.e. Single value (A,B,C,D...U,V,W,X,0,1,2...8,a,e...)

Whereas for the field SOBKZ -data element SOBKZ-Domain SOBKZ-Special stock indicator has the Value Table T148.

Please let me know How to decided when should we go for single or Value Table

for a Value Range given for a Domain

Thanking in Advance!!!

Thanks,

PK