Well, 30+30 equals 60, right?
The problem is that various accounts imply that there were 30 men on a side in addition to the commander himself. Were there 31 on a side for a total of 62?
About 100 years ago, H.R.Brush edited the most detailed account, a product of Brittany and therefore written by someone well acquainted with the battle, and he concluded that there were 30 participants on either side. In my article, my chapter in the book deeds of arms, and in my source reader on the combat, I followed Brush.
But, at about the same time that I finished my source reader (called the Combat of 30, volume 2 of my series Deeds of Arms) , Michael Jones wrote an article called "Breton soldiers from the battle of the 30 (26 March 1351) to Nicopolis (25 September 1396)," which appeared in Adrian R. Bell et al., eds., The Soldier Experience in the 14th century (Boydell Press, 2011). Jones was very interested in the careers of Bretons in the first half of the Hundred Years War, and the best examples he could find were the men at the combat of the 30. He followed them as closely as he could, and he was able to find a quite a bit about them, at least about those on the pro-French side.
And he came to the conclusion that there were 31 on a side.
I have not gone through his list systematically hecking It against Brush's (in Modern Philology).
I'd love to farm this out to Will McLean but alas he is not available.