To find two details about Anne Frank’s character that are revealed through her story on her math teacher, Mr. Keesing, one will have to find the part in her diary where Anne describes her relationship to Mr. Keesing. Keesing appears early on in Anne’s diary; he’s discussed in the entry labeled “Sunday, June 21, 1942.”
After discussing the anxiety that the class is experiencing over which students will be promoted and which will have to stay back, Anne turns her attention toward her teachers. She says she gets along “pretty well” with most of her teachers, yet there's discord between her and Mr. Keesing.
According to Anne, Mr. Keesing was upset with Anne “for the longest time” because she “talked so much.” The source of Keesing’s irritation reveals one detail about Anne’s character: she likes to talk. In fact, Anne likes to chat so much that, eventually, Mr. Keesing makes Anne write an essay about being a chatterbox.
In her essay, Anne cheekily ascribes her talkative character to gender and biology. Her mom, when she was young, talked as much as Anne did, and there’s nothing Anne can do to counter “inherited traits.”
The humorous tone of Anne’s essay, particularly her depiction of Mr. Keesing as an “old fogey” shows something else about her character: that she has a sense of humor.