I'm not sure if this was the best thing you could possibly do but here's what I did for each of mine:
1. Elaborated on my roles and talked about what I learned from them. Talked about my passion for music, etc.
2. Related it to personal statement and why it was meaningful.
3. Finished describing the experience (because it was research and difficult to explain fully in 700 characters) and talked about how it required some perseverance and independence.
I'm also not sure how much weight med schools are going to put on those descriptions because it's the first year of having them.