When reading a question here on MSE just yet, I noticed this. Instead of the number 15, the badge count is written as a word.
I haven't found any other instance that replicates this.
This happens when the page is automatically or manually translated to English. Since there was Russian text in the question you linked, Google gave me an option to switch between translations. After translating to English, the result was the same as in your case:
This has been a known issue on non-English sites. For example, see: Vietnamese to English translation issue and Google Translate, languages, and numbers oh my!. This is not an issue from SE's side, but from Google's side. See: "Numbers translated into words (undesired)" on Google Translate Help Community.