Client Tools :: How To Have Column Heading As Example Of Substr Function

I would like to have a column heading as follows in double inverted comma. but sqlplus environment returns column heading length equal to output value.

SQL> select substr('The independence day', 5,12) "Example of substr function" 2 from dual;

Example of s
------------
independence

I know that default column heading length is 30 character long.

but my column heading is less than 30 character long (which is 26)

How can i have column heading as Example of substr function?