It sounds normal. It removes records in chunks for five minutes only to avoid impacting the site's performance.
If you've changed Log Table Cleanup's schedule to run every ten minutes you would be better off manually deleting the records with an SQL statement instead. This is described in the link in this previous reply, for example (MySQL/MariaDB):
DELETE FROM mdl_logstore_standard_log WHERE timecreated < UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 60 DAY));
Back up the database before making changes like this. This statement may take some time to complete and adversely affect site performance while it's running.