expdp with flashback_scn returned same dump file size as without flashback_scn

Dear All,

I am exporting some tables of the database using expdp with flashback_scn. The dump file size is same as if I execute the expdp command without flashback_scn. Can anyone please help me that why the size of dump file is same? I did following steps:

1. select DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER from dual;

2. Waited till all the transactions disappeared from gv$transaction where STARTSCN_B is less as the flashback_scn returned above.

3. select DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER from dual;

4. expdp <user>/<pass> tables=<table_names> director=<directory_name> estimate_only=y flashback_scn=<flashback_scn returned from step-3>