In Volume 1, Book 5, Chapter 8, the narrator describes how King Arthur defeats Emperor Lucius and the Roman army. After Arthur slays Lucius himself, the narrator uses a hyperbole to support Arthur's status as a great king:
And when it was known that the emperor was slain, anon all the Romans with all their host put them to flight, and King Arthur with all his knights followed the chase, and slew down right all them that they might attain.
And thus was the victory given to King Arthur, and the triumph; and there were slain on the party of Lucius more than a hundred thousand.
The idea that Arthur and his knights manage to kill more than 100,000 men is incredible. In fact, this number is so incredible that it seems to be included less for a sense of historical accuracy than to make Arthur seem like a greater warrior than the world has seen before or since his time. The hyperbole suggests that Arthur is not only incredibly strong and talented, but also that he is a fantastic leader.
It is important to note that many of the people in Lucius's army are "Saracens," or Muslims. The hyperbole about the number of people Arthur and his knights kill makes Arthur appear as not only a superhuman military leader, but in particular as a superhuman Christian military leader. Arthur's authority as a king relies on his ability to rally knights on the side of Christianity, even to the point of killing non-Christians en masse. Arthur is supposed to have lived centuries before the Crusades, a series of religious wars in (roughly) the 12th and 13th centuries. In the Crusades, Christians (most of the time supported and funded by the Latin Church) fought Muslims to take control of religious sites. Malory is writing in the 15th century, after the Crusades but in the midst of their cultural aftermath. Arthur's characterization in this scene seems to be trading on anti-Muslim sentiment and a post-Crusades nostalgia for great Christian leaders.