I am applying for a PhD in a highly theoretical field. One of my recommenders, a faculty in the field, understands that I have a unique situation when it comes to applying for grad school, so he has given me some advice on how to write my statement of purpose. He suggested that I read a certain series of lecture notes in this field in order to find a very specific topic in this field that interests me, then write my SOP about that topic.
The problem: I have read the notes and they are all far beyond my level. On one hand, I want to tell my recommender this and ask whether he has any advice regarding an alternative approach for writing my SOP. On the other hand, since he is my recommender, I worry that asking him this would reveal that I am not as smart as he thinks I am, which would make his recommendation less strong. What should I do?