When you are building your SMS dialogs you can send messages that are bigger than 160 characters, which is the maximum number of characters that can be sent in one SMS.
In Service Studio you can handle messages with a maximum of 320 or 480 by simply setting the Length property. How?
In this situation, instead of sending one SMS, Platform Server sends two SMS messages (320 characters) or three SMS messages (480 characters).
Send Message Properties