The flag indicates whether field inserted in the database is to be filled with initial values. The initial value used depends on the data type of the field. I.e. type n(2) is '00'.
When you create a table, all fields of the table can be defined as NOT NULL and filled with an initial value. The same applies when converting the table. Only when new fields are added or inserted, are these filled with initial values. An exception is key fields. These are always filled automatically with initial values.
