Reports & Discoverer :: Order The List Of Value?

I am using oracle 6i and i have parameter. I want the value of parameter to be sorted i use the following query

SELECT DISTINCT To_Char(LD_TASK.TASK_ID) DISPLAY_COL1
FROM LD_TASK
UNION
SELECT '%' DISPLAY_COL1
FROM DUAL
order by display_Col1

In the output i get the value sorted but according to just the first number how i could make it according to the hole number

example of the output
1
11
12
13
14
6
7
8
9