follow-up article control type

Hi all,

I'm customizing the follow-up article process and specially the substitution profile.

I've done some tests with control type "Event-controlled" and "Time-Controlled" and it's works well when the delivery is created.

But when i use control type "Initial" nothing appends.

I don't understand what is this control type ? and in which case i can use this control type ?

Somebody can explain to me ?

Thanks for your response

Regards

Eric