Structure of traffic data in burst_ind messages

I'm experimenting with burst-ind branch and am able to track control messages in ccch_scan. I then send an Assignment Command to change to a traffic channel. I can see the bursts come in, but cannot make out the format of the data. If I understand right, the burst_ind structure holds 15 bytes of data, but the traffic data should be 33 bytes. I assume the traffic data is spread across several burst-ind messages. Can you please clarify how to re-assemble the full 33-byte traffic data structure from the burst_ind messages? Thanks. B.