Four digits may be stored to the right of the decimal point for the second.
SQL> CREATE TABLE mytimestamp (
2 id INTEGER,
3 made_on TIMESTAMP(4)
4 );
Table created.
SQL>
SQL> INSERT INTO mytimestamp (id, made_on) VALUES (
2 1, TIMESTAMP '2005-05-13 07:15:31.1234'
3 );
1 row created.
SQL>
SQL> select * from mytimestamp;
ID MADE_ON
---------- ---------------------------------------------------------------------------
1 13-MAY-05 07.15.31.1234 AM
SQL>
SQL> drop table mytimestamp;
Table dropped.