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The example name indicates it is the second release of buildroot (the artifacts) based off the 2019.08 version of buildroot (the tool).  Note that it does not indicate when you built this version.  You may have built it today but you based it off a version of buildroot from 2019 (or whenever).

We've never had a second release before, so you'll not see -1 or -2 in any of the names, except the version I am working on as I write this doc.

The "ipxe" directory under "boot" contains file for every machine that boots buildroot.  The filename indicates the machine name.  In that file you will find a line like this:

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You can modify that line to point at whatever version of buildroot you would like, including a test directory.  Your test directory must not be in a mounted directory (like AFS) as the machine booting won't be able to access mounted file systems.  For this reason, if you have a test directory, it's probably best for it to be in this ("boot") directory.

Versions

There are many versions that get baked in to buildroot.  There is a BusyBox version, a kernel version, a Preempt RT patch version, user tools versions, and of course a buildroot version.

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Buildroot versions can be found at their downloads page.

The current version that we use (2019.08) is here.