Don't worry about that, this doesn't affect you.
When Jeff wrote uboot scripts he described some ways of linux installation, included install an ubifs in mtd3. When system boots up it tries to boot from, in this order: rescue usb, normal usb, mtd3, mtd1 (rescue system or pogo default firmware). In your case, when you boot up your system whitout any usb media on it the system finally boots up in the rescue system after a few warnings on the serial (or netconsole) port.