IVR Studio lines required for 4-line autodialer

I am running a 4 lines BBP Professional version for appointment reminders. Currently the settings are

Press 1 to repeat, press 2 to confirm and press 3 to reschedule. So when the patient/receiver press either one, they will immediately hear “Thank you and Goodbye.”

Now what I want is that after the receiver made the choice, there will be an end message like “Thank you for confirming your appointment with us” or “you have requested to change your appointment, our staff will contact you within the next working day” or “you have request to cancel your appointment, our staff will contact you within the next working day”

So if IVR can craft out this message, how many lines of IVR do I need JUST for this purpose?

You need one line IVR Studio. The lines licensed with IVR Studio is for inbound applications. You have 4 licensed lines for outbound applications through BBP autodialer already.