To decode the extended information, refer to Section 7.1.1 f the ANT Message Protocol and Usage Document. You need to look at the flag byte (byte 9), which is 0x80. This indicates that the extended information includes just the channel ID, as outlined in Section 7.1.1. I am puzzled on why you are getting such a long message there tho. Was anything else modified other than the channel parameters?
Note however that the USB2 does not support RSSI measurements (and neither does the USB1 or USBm). If you are interested in obtaining RSSI measurements, you will need to use hardware with this capability, such as the C7.