Sequence for running BoM Planning

As my understanding, once the user enters the end date of the production proposal, system calculates the start date of production from the end date.

However, the user wants to enter the start date of production and wants the end date of production to be calculated.

Thus, I am trying to edit the start date of the production proposal after the production proposal has been made.

But I don't know when I have to run a single BoM planning.

Two cases in which single BoM planning runs in different order are as follows.

Could I ask which case of scenario is correct?

Case 1.

"Run single BoM Planning" -> save -> "Change of start date" -> Save -> Release

Case 2.

"Change of start date" -> save -> "Run single BoM Planning" -> Save -> Release