When sending an SMS in Assignar, the number of characters you can have per SMS message is 305 characters. The reason is that a standard SMS is 160 and you are given an allowance every month for outgoing and incoming SMS. This restriction helps ensure that you don't go over this allowance.
If you do need to send more text then we suggest writing Part A at the top of your SMS and then send, compose a new one with Part B.