SQL & PL/SQL

BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE	11.2.0.3.0	Production
TNS for HPUX: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production

CREATE TABLE mytable
(
  JOB_REQUEST_ID       NUMBER(10),              
  USER_ID              NUMBER(6)   
);

SET DEFINE OFF;
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610756, 7926);
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610756, 8318);
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610757, 7926);
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610757, 8318);
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610758, 7926);
Insert into MYTABLE
   (JOB_REQUEST_ID, USER_ID)
 Values
   (4610758, 8318);
COMMIT;

this works fine for a comma delimited list

SELECT job_request_id,
         LISTAGG (user_id, ',') WITHIN GROUP (ORDER BY user_id) user_ids
    FROM mytable
GROUP BY job_request_id;

JOB_REQUEST_ID	USER_IDS
4610756	7926,8318
4610757	7926,8318
4610758	7926,8318

however I'm getting an error when trying to select it into a varray I'm not quite sure what I am doing incorrectly.

 SELECT job_request_id,
         CAST (COLLECT (USER_ID) AS SYS.OdcinumberList) user_ids
    FROM mytable
GROUP BY job_request_id;

ORA-22814: attribute or element value is larger than specified in type