I've been searching around, but I can not find a good explanation (or understanding) what the 'time' value in hook_cron_queue_info actually does, or how to set it to work properly.
it is said that: 'time': (optional) How much time Drupal should spend on calling this worker in seconds. Defaults to 15.
I don't quite understand that. Does calling the worker mean time allowed to execute the cron queue job? And does the next cron queue job starts after this time? Or when the previous job is completed?