When loading table schem with default values, it quotes the values of some (randomly)

See and compare the default values of "EXPCKFLAG", "XMLCHECK", "ENFSEDFLAG" from the first table,
and chec the default value of NULL with unnecesaary quote n the column "ATTFILEFLAG" in the 2nd table.

CREATE TABLE "BMS_CODE"(
"CODEID" character varying(10),
"CODENAME" character varying(200),
"TCODEID" character varying(10) DEFAULT 'N',
"USEDFLAG" character varying(2) DEFAULT 'Y',
"DESCRIPTION" character varying(1000),
"INID" character varying(70),
"INDT" character varying(28),
"UPID" character varying(70),
"UPDT" character varying(28),
"MODIFYFLAG" character varying(2) DEFAULT 'Y',
"DISPLAYFLAG" character varying(2) DEFAULT 'Y',
"ACKFLAG" character varying(2) DEFAULT 'N',
"EXPACKFLAG" character varying(2) DEFAULT '''N''
',
"APPVLFLAG" character varying(2) DEFAULT 'N',
"XMLCHECK" character varying(2) DEFAULT '''Y''
',
"ENFSENDFLAG" character varying(2) DEFAULT '''N''
'
);

CREATE TABLE "BMS_DCT_FAXSND_HIS"(
"DOCID" character varying(70),
"RECEIVERID" character varying(70),
"SNDORDER" numeric(3,0),
"RECEIVERNM" character varying(512),
"RECEIVERSEQ" numeric(4,0),
"FAXNUM" character varying(40),
"SNDREQDT" character varying(28),
"ATTFILEFLAG" character varying(2) DEFAULT 'NULL',
"SNDREQID" character varying(70)
);