The update function in LE settings checks official servers for official LE images. We have never released an image for generic Android boxes so you must be running something community created; hence nothing is listed when you check for updates. Some of the community image creators also take liberties with version numbers and content, which explains why 8.0.2 on your box does not have Kodi 17.3 like our official 8.0.2 release.
I've moved the thread to the Amlogic section of the forum where the offending community creators hang out