This ‑e is an adverb ending. The belonging adjective is «latinus» ‹Latin›.
Interestingly, the language adverbs are also used in a construction with scire (to know) or intellegere: "Latine scit" (he or she knows Latin), "Graece intellegit" (he or she understands Greek). In English we would definitely think of this as needing a direct object, but Latin allows it as an adverb, to understand "in a Greek way" (perhaps it would make sense to think of it as something like "in a Greek manner" or "from a Greek perspective").