If you look at the your EBCDIC data file (input file), and the actual field you are adding leading zeros to, you will find that the "curly left brace" is there. That is because the field is a "zoned" (PIC S9) not an unsigned numeric (PIC 9) that leadzero.cus was designed for.
You will need at least our EBCDIC level 2
package to convert this field, and then
define the field in your .LAY file like this:
z c1,c2 z
The 1st z defines the columns c1-c2 as
a zoned field, the 2nd z specifies that
leading zeroes are to be added to the
ASCII output for this field.