Unifi ac ap lr Install question

Hi Guys,
I'm new here. I have the round version 2 of this unit and am wanting to install OpenWRT on it. The first line of a MTD instal lsays "Obtain the Unifi Firmware version 3.7.58 for your device" My firmware version is

The command: fwupdate.real -m /tmp/ubnt.bin
Shows: Invalid Image MAGIC ''V'

Question is how do I proceed form here? Do I DOWNGRADE the firmware image to 3.7.58?