can't sort data in Postgresql data type json

I'm currently trying out the "new" data type json. This is part of the definition as php Array (one row of data that is stored in the field)

'processed'=>array(5):
        ["ct"]=>
        int(1)
        ["wt"]=>
        int(11)
        ["cpu"]=>
        int(0)
        ["mu"]=>
        int(1056)
        ["pmu"]=>
        int(0)

I tried the following query:

SELECT id, data->>'processed'>'ct' as sortField FROM system_debug ORDER BY sortField ASC

but all I get in return is an table like this:

id  sortfield
    6   true
    7   true
    8   true
    9   true
    10   true
    11   true
    12   true
    13   true
    14   true
    15   true
    16   true
    17   true
    18   true

I'm trying to implement Sorting without the needs of storing the data seperatly inside the table. Where am I mistaking?

Table Scheme:

                CREATE TABLE system_debug (
                    data JSON,
                    id integer NOT NULL
                );

                CREATE SEQUENCE system_debug_id_seq
                START WITH 1
                INCREMENT BY 1
                NO MINVALUE
                NO MAXVALUE
                CACHE 1;

                ALTER SEQUENCE system_debug_id_seq OWNED BY system_debug.id;

                ALTER TABLE ONLY system_debug ALTER COLUMN id SET DEFAULT nextval(\'system_debug_id_seq\'::regclass);

I appreceate any help that I can get ^^