Estimating the number of ancient texts that were produced is difficult since they were written on various media, and most haven’t survived to the present day. According to one source, “Scholars often estimate off-the-cuff that around 1% of the known works written in Greek and Latin in ancient times has survived to the present day.” Even fewer survived that were written in other languages.
Still, we can arrive at a very rough, ballpark figure by noting that at the Academy for Ancient Texts, there are around 2,000 ancient texts available online, with several hundred more waiting to be coded.