First, let me point out that your question is not related to the topic of this forum, which is learning disabilities. Nevertheless, I can ensure you that there is nothing wrong with your younger sister, the behavior your describe is quite natural for teenage girls or young adults. Think of her note as a mini-diary, most adolescents have one. While you may not be able to decipher the meaning of the numbers, the general idea of the note is quite clear. You obviously care about your younger sister and assumed parental role with her, yet I would strongly advise you against going through her personal items - it is guaranteed to damage your relationships, if discovered.
Dr. Tali Shenfield
Thanks Dr. Shenfield but the book was not a dairy and i was not going through her stuff. its a book that i give to her to complete activities. therefore whenever she is through with the book she always returns it to me. so upon her returning it to me, i saw the scribble.