I didn't go this route but they're most likely to ask about your general history, what was school like, when you felt this way, how your family is. I went to a gender therapist and this is what she asked me first. Btw, I also worried about saying the wrong thing and not being 'trans enough' for them. A competent therapist will know that it is ultimately our decision and if we have some sort of discomfort in our current assigned gender then we're most likely on the trans spectrum.
You'll be fine, good luck 🙂