Weird behavior of 'default user'

Hello!

Look at this:

------------------
adb=> create table hh (dd char(2) default user, ff int4);
CREATE
adb=> insert into hh (ff) values (5);
INSERT 572034 1
adb=> select * from hh;
dd |ff
----+--
leon| 5
(1 row)
------------------

How can I understand that? Column dd is of type char(2), whereas
'leon' is four characters! Even more, look here:

------------------
adb=> insert into hh values (user, 7);
INSERT 572045 1
adb=> select * from hh;
dd |ff
----+--
leon| 5
le | 7
(2 rows)
------------------

This absolutely beyond my mind. This means that user, being
inserted explicitly, is correctly truncated. If it is inserted
by default, it is wider than column! Seems something very strange
is going on here.

--
Leon.