Did you save the numbers as text?
because if you follow the instructions for a column integer like in the following url:
sorting rows[
^]
you get the result you want.
If it is text use:
Select WindowsNo from Table1 where ProjectName='" + PjtName + "' order by (WindowsNo + 0) asc
The (field + 0 ) converts the text/character in the field into an integer.