When you turn on Reminders for the first time, Satago will, the following day, attempt to send the appropriate reminder in accordance to the invoice due date.
You turn on Reminders for the first time.
You have an invoice that is currently 6 days overdue.
Satago will, the following day, send the Reminder 2 template, which is normally sent when an invoice is 7 days overdue (by default, but please feel free to change the trigger days here). The information in this reminder will be correct for the day it is sent.
If the invoice becomes 14 days overdue Reminder 3 will be sent then next week.