premacro vs. postmacro

Question, I have some actions in the premacro, I know that everything in the premacro has to be done before GSE moves on to the main sequence, but how does postmacro work.

By its name, it implies that it will be executed AFTER the premacro, so on that assumption, I put some actions in the postmacro that I want done AFTER everything is done in the premacro, but it seems that the postmacro is executed alternately with the premacro!?

How does it work (what is the flow supposed to be?)