How is Suggest Reminder Lines batch works

Dear all,

I am trying to run the suggest reminder lines batch job from reminder page. I want to know what formula system uses to populate the lines in reminder lines.

Ex: Inv0001 Due date = 22/10/22
Inv0002 Due date = 28/10/22

Now I have set 3 levels of reminders 1st level +5D 1Addnl Fee =$10
2nd level +7D Addnl Fee = $15
3rd Level +10D Addnl Fee = $20

Now my understanding is when I run suggest reminder lines batch , system should populate level 1 as Inv0001 since todays date is 28/10/22 and Level 2 as Inv0002 . Is the due date calculation based on todays date or is it based on document date given in reminder header . Please tell me the formula which suggest reminder lines batch uses for populating the reminder lines.

Thanks in advance.

Regards,
sekar.