That's one problem with relying on automatically extracted information - sometimes it's not really what you want. In this case that's just what GitHub puts in the og:description tag for large? repos, probably to make it appear that way on Google. Of course I could fix it for this instance but then it wouldn't really accurately represent what you can expect...

The relevant code to extract that is a Zotero Translator [1] so that's what would have to be changed for this.

[1]: https://github.com/zotero/translators/blob/master/GitHub.js