Help writing a waitlist letter of interest

I was recently waitlisted at a top choice of mine (no, not an ivy or top 20). I am writing them a letter to say that their school remains my top choice and to show demonstrated interest. How do I subtly mention the fact that my gpa is slightly lower than what they want (I have a 3.66 uw) because my high school is ranked top 30 in the US and has a pretty difficult curriculum?

Don’t mention those things at all. Only update them on what you’ve been doing and affirm (if you can do so honestly) that if you’re accepted you will attend. @Freeholder