Another Error by Harvard Professor?

 I'm not really picking on Prof. Lepore, not much anyhow. She writes really well. But as I've said before I do enjoy finding errors.  This time it's page 109 of her book "If Then: How the Simultanics Corproation Invented the Future".  She's writing about the dance among Arthur Schlesinger, Jr (another Harvard professor who wrote well), Adlai Stevenson, and JFKennedy in 1960.  Stevenson is vacillating as usual over whether to run for president, and JFK is trying to keep him out, with Schlesinger in the middle. 

In two separate paragraphs she describes meetings between Stevenson and JFK, one on May 21, one in "late May" which was arranged by Schlesinger.  I have to believe it was one meeting, but the way it's written it sounds like two. I suspect she tried to describe the meeting in separate drafts which didn't get cleanly merged. 

I've not finished the book, but am enjoying it, as I remember the maneuvering then, much more fascinating than today's politics.