You are correct that the question is poorly worded / defined. Mostly it doesn't matter. In some fields (such as IM), it's traditional for applicants to have a "Chair" letter. Which is almost never actually written by the chair, but instead is a summary letter from the Department about all of your experiences there -- usually your clerkship, SubI, and ICU or electives. It's like a mini-MSPE. Often completely useless if you're coming from a DO school, or if an IMG. It hopnestly doesn't matter what you pick, people will just review all of your letters.