Not receving report for every cron (processsq)

[buster13]

crontab */20 * * * * (processq)
there are bounce emails entered to my declared
$message_envelope = 'bounce...." in config.php
the phplist is also blasting (saw the numbers going down in browser view)

-config.php-
define ("MANUALLY_PROCESS_QUEUE",0);
define("MAILQUEUE_BATCH_SIZE",0);
define("MAILQUEUE_BATCH_PERIOD",900); // 15min < 20min cron
define('MAILQUEUE_THROTTLE',6);

i did SET correctly my email address to receive report (been doing phplist > 3yrs) but did not find any report mails not even in SPAM folder.

log shows it is blasting newsletter correctly but in hourly manner - not sure why not 20min and the event log shows 11pm, 2am, 4am . (funny it is not even a CONSTANT 1hr log)
i should receive blasting report every 20min right according to my cron time?