exim -bP strangeness

exim-1.58. When I say 'exim -bP all' I see some strange things.

----------------
...
delay_warning = 1d
-1
delivery_date_remove
...
no_queue_only
-1
queue_run_max = 5
...
smtp_connect_backlog = 5
-1
smtp_receive_timeout = 5m
-----------

What are these '-1'?