Tris has a childhood memory of going to the hospital with her mother—what does this memory reveal about Caleb as a child (that Tris never realized before)?

Tris recalls the first time she was in the hospital at six years old, when her mother fell and broke her arm. An Amity nurse set it, and Tris remembers Caleb telling her it would mend quickly because it was a hairline fracture, and she wonders if this was his secret Erudite studies showing through.