Hermione had to cover her mouth with her hand to keep from gasping at her son's observation. Sometimes it was easy to forget that he was intelligent and perceptive. The adults in his life weren't aways very careful about guarding their tongues in his presence. While she couldn't specifically remember any moment she'd mentioned her past with Augustus where Oliver could hear, clearly she hadn't been as aware as she thought. In an effort to keep the moment from being awkward, Augustus laughed.