Amazon Firestick Gen2- What build to use?

I am trying to update Kodi to Krypton 17-beta on a new Firestick (gen2) and am not sure if the android ARM 32 bit version is the appropriate one or the 64bit version. I have already put the older Alpha release on the device using the Firetuner app but am running into issues with confluence skin compatibility and hence the update. I am unable to determine which version(32/64 bit) the Alpha release is( Kodi 17.0-ALPHA2 Git:2016-06-30-f3ca4ea compiled: Jun 30 2016.