To change DBIO_EXPECTED for EM

 SELECT parameter_value,is_default FROM dba_advisor_def_parameters WHERE advisor_name = 'ADDM' AND parameter_name ='DBIO_EXPECTED';

EXECUTE DBMS_ADVISOR.SET_DEFAULT_TASK_PARAMETER('ADDM', 'DBIO_EXPECTED', 20000);

select * from aux_stats$;