No, it is not Google Analytics. It is Google Search Console:https://search.google.com/search-console/
This is a place where you as an administrator of the service can see what is the result of google bot crawling your site.
Each entry in the report is a separate URL which google crawler stores during the indexing process.
Each URL is then classified as correct, duplicate, Error 404, etc.
The main functionality of Google Search Console is to show you how google sees all pages of your web site. Duplicates are reported as warning because a web site uses 2 or more different links to point to exactly the same content, what Google considers as a mistake. That impacts negatively the "quality" of your web site, causing it will be de-prioritized by google search engine when showing results.
And you are right. It is not a functional bug if we only think of JDownloads as a service to publish files. Unfortunately this feature of jDownloads should be corrected to work properly with google, so jDownload pages do not cause google score is negatively impacted.