Here you're talking about a set of Installers, not Ruby itself.
I've answered your question over Stackoverflow:
Which I'm going to copy here for the sake of help others find the
information in the future:
"Hello,
Ruby-Lang website advertise a package of Ruby for Windows called One-
Click Installer.
That installer used to have their own version schema, as you note with
`186-26` or `186-27 RC2`
On RubyForge website (news section) you will find that efforts of the
project as moved towards newer RubyInstaller packages, and is
indicated there and the RubyInstaller download page that `186-27 RC2`
is part of the legacy versions.
Latest RubyInstaller (currently in Release Candidate attempts) provide
information of the correct Ruby version that includes and install, as
indicated by the version string `1.8.6-p383` which is patchlevel 383
of Ruby.
Please note that you're comparing different type of packages. One-
Click Installer versus RubyInstaller.
You can read more about this in the [wiki][1] and the latest
announcement [at RubyForge][2]