What is the purpose of enabling "Answer confirmation for offnet numbers" in Simultaneous Ring Logic, and what steps are involved?

Purpose for Anser confirmation for offnet numbers

Enabling this option provides audio confirmation when the call is answered by an off-net number, requiring checking "simultaneous ring" and adding at least one off-net number. This can be done by also checking "ring all user's phones" or by adding a 10-digit or 11-digit number at the bottom.