That’s essentially a hash/checksum of the source files used when compiling Caddy. It’s a good way to compare whether the version you’re using had modified code compared to another binary someone else might have.
In general, you can ignore it, but it’s helpful for us when asking for help here in the forums so we can notice if you’re using a modified version, instead of an official release.
This part is the more relevant bit. This is information from git at the time the binary was built. It’s telling us it was built from commit https://github.com/caddyserver/caddy/commit/fe91de67b62c, the timestamp on the commit, and the “closest tag” in front, i.e. v2.6.2. This is correct, that’s the commit we tagged with that release.
You are using the latest. You can tell by that v2.6.2 in the front of the version string.