That's the build that's on there already. It recognizes it as a RC bit it's recommending that a 'stable' build be installed.
It is already the stable version.
You can basically just change the version in this file https://github.com/JamesLinEngineer/RKMC/blob/Jarvis/version.txt and build your own Kodi.
You can also unpack the app with an Android apk decompiler and just change that file if the message bothers you.
RKMC Kodi 16.1
https://github.com/JamesLinEngineer/RKMC/commits/Jarvis?after=GWjtZC6zmLRUhdP0ef8Vwn24uUYrMzQ=
Kodi 16.1
https://github.com/xbmc/xbmc/commits/16.1-Jarvis
You can see there are only 2 differences Kodi 16.1 has namely the version number change and cuesheet that RKMC 16.1 doesn't have compared to all the extra changes RKMC Kodi has to improve playback.
If you install a different Kodi you will loose lots of optimizations like HD Audio, 3D, auto frame-rate switching and smooth 4K playback.
If you want, you can also try Kodi 17 beta 2 with added dts/ac3 pass-through support for RK3229 if you don't use the other features.
http://ftp.halifax.rwth-aachen.de/x...kodi-20160925-c9ce17b-amlugly-armeabi-v7a.apk