Greetings cwong668,
Thanks for visiting the Apple Support Communities! It seems you're curious how to remove a Bluetooth accessory listed in the Other Devices section of the Bluetooth settings on your iPhone.
The devices listed in the Other Devices section are Bluetooth accessories that are seen by your iPhone to be in pairing mode. You're unable to remove these devices from your iPhone, and the devices would need to be either powered off or pairing mode disabled for them not to appear in the Other Devices section of the Bluetooth settings.
It looks like the Mi Box is an AndroidOS streaming device. If that's yours, you may wish to view the manufacturer documentation for pairing details.
Pair a third-party Bluetooth accessory with your iPhone, iPad, or iPod touch - Apple Support
Kind regards.