Apex Programming Defer statement peculiarity

[Exus]

I have a question regarding programming, specially for the "Defer" statement.

This is the example code for programming the AFS given in the manual.

[v-feed]
Set OFF
If Time 12:00 To 12:01 Then ON

[skimmer]
Set ON
If Outlet v-feed = ON Then OFF
Defer 15:00 Then ON

[return]
Set ON
If Outlet v-feed = ON Then OFF
Defer 10:00 Then ON

[feeder_3_1]
Set OFF
If Outlet v-feed = ON Then ON
Defer 1:00 Then ON

For the [feeder_3_1], the Defer statement ignores "If Outlet v-feed = ON Then ON", before turning ON after 1 minute.
But for [skimmer], the Defer statement acknowledges "If Outlet v-feed = ON Then OFF", before turning ON after 15 minutes.

Why is it that the skimmer is turned off, but the feeder isn't turn on right way, when both are followed by the defer statement?

It seems that the Defer statement performs differently based on if they have matching ON/ON or OFF/OFF states.

 

[Exus]

Solved.