Calibre enforces a maximum path length when sending to devices. IIRC that max is around 225-250 characters. If a path is longer than that then calibre takes characters out of the middle of each path segment until the path "fits". In your case "Fiction" became "Fn". I suspect that the "es" was "ebooks".
You can use the "
shorten" template function to ensure that the length of {title} - {authors} is less than some amount. Perhaps you might want to apply shorten separately to each of title and authors. Another possibility is to use only the first author. Up to you.