Did you add this code in the "Conditions" box ?
If yes the please enable the "Debug" feature under the frontend/admin listing areas and post the debug statements here.
Yes, I did it under "Conditions" box. Now, there is the result of your suggestion (I've enabled the debug in Admin list):
Array
(
[0] => SELECT `Extension`.`id` AS `Extension.id`, `Extension`.`name` AS `Extension.name` FROM `j25_chronoengine_extensions` AS `Extension` WHERE `Extension`.`enabled` = '1' ORDER BY `Extension`.`ordering` ASC
[1] => SELECT `Connection`.`id` AS `Connection.id`, `Connection`.`title` AS `Connection.title`, `Connection`.`params` AS `Connection.params`, `Connection`.`extras` AS `Connection.extras`, `Connection`.`published` AS `Connection.published` FROM `j25_chronoengine_connections` AS `Connection` WHERE `Connection`.`title` = 'INSERZIONI_CERCO-OFFRO_LAVORO' AND `Connection`.`published` = '1'
[2] => SELECT COUNT(`annunci`.`id`) AS `annunci.count` FROM `j25_cf_v5_INSERZIONI_CERCO-OFFRO_LAVORO` AS `annunci` WHERE `annunci`.`approvato` = '1'
[3] => SELECT `annunci`.`id` AS `annunci.id`, `annunci`.`created` AS `annunci.created`, `annunci`.`titolo_inserzione` AS `annunci.titolo_inserzione`, `annunci`.`tipologia` AS `annunci.tipologia`, `annunci`.`categorie_professionali` AS `annunci.categorie_professionali`, `annunci`.`tipo_di_impiego` AS `annunci.tipo_di_impiego`, `annunci`.`nome_azienda_studio` AS `annunci.nome_azienda_studio`, `annunci`.`email_utente` AS `annunci.email_utente`, `annunci`.`inserzione` AS `annunci.inserzione`, `annunci`.`approvato` AS `annunci.approvato` FROM `j25_cf_v5_INSERZIONI_CERCO-OFFRO_LAVORO` AS `annunci` WHERE `annunci`.`approvato` = '1' ORDER BY `annunci`.`id`, `annunci`.`created`, `annunci`.`titolo_inserzione`, `annunci`.`tipologia`, `annunci`.`categorie_professionali`, `annunci`.`tipo_di_impiego`, `annunci`.`nome_azienda_studio`, `annunci`.`email_utente`, `annunci`.`inserzione`, `annunci`.`approvato` LIMIT 30
)