If there are already existing items in the queue the queue based trigger gets triggered. Say even if you stop your process after processing 17 and only one is left as your minimum is one… the job gets triggered after sometime which is 30 minutes or whatever you set in config as yours is on prem… so even if no new item is added because of existing new items the queu based trigger is searching after some time and triggering it
Hope this clears
Cheers