In To Kill a Mockingbird, when Atticus asks Scout about the blanket around her shoulders, what does Jem realize?

In Chapter 8, Miss Maudie's house catches on fire in the middle of the night, and Atticus tells Jem and Scout to stand in the Radleys' yard while he and the other neighbors attempt to save Maudie's furniture. While they are standing in the yard, Boo Radley silently approaches Scout and puts his blanket over her shoulder without her knowing. The next morning, Atticus asks Scout who gave her the blanket. Both Scout and Jem are perplexed. Atticus then tells them that Boo Radley was the person who covered Scout with his blanket. Scout says she almost threw up out of fear, and Jem promises his father that he won't attempt to bother Boo anymore. After learning that Boo tried comforting Scout, Jem realizes that Boo Radley is not a threat. Jem finally understands that Boo is not the "malevolent phantom," and believes Boo was responsible for sewing his pants the night of the raid.