The "Send a copy to admin" option sends a copy of the outgoing text to the admin just prior to dispatching all of the other texts. Many clients will choose this feature to simply see that their texts are actually going out on schedule. When using the event invite app it can also be nice to have a copy of the invite sent to you, the admin, as this means you can optionally reply LIST to see who has RSVP'd for the event in the days coming up to the event.