In SamBroadcaster /stream is represented by SID 0 , /stream2 is SID 1, etc.
You can find "SID" in SAM Broadcaster right where you fill in the IP, port, stream password, etc.
Just to be clear, you need to create two encoders in SamB. One for SID 0 at 128kbps MP3 and one for SID 1 at 62kbps AAC