Hello. Let's take it in order:
This command literally means a delay before CH47 appears on the edge of the map after the spawn event.
"Delayed departure of CH47 after the start of the event [sec.]"
If on your map CH47 will fly to the event in 5 minutes, the departure delay of CH47 is 0.0, the time of the event is 1 hour (3600), and the notification time before the end of the event is 120.0, then when starting the event without any interaction with it, CH47 will arrive in 5 minutes, scarecrows will enter it and he will fly away, the timer for the end of the event will change to 120 seconds. Based on these data, I believe you need to choose the right values depending on your wishes.
"Duration of the event [sec.]"
"Notification time until the end of the event [sec.]"