I wish we had 20 slots.
Or just one more slots to fit in my presentations/posters....
Or a slot to tell medical schools to just accept me already.
I noticed that this thread has SO MANY QUESTIONS, but not as many answers. I will give my suggestions to take a break from my application editing process, but these are just my suggestions.
I would put the latest end date, and make sure you explain in the description that you are planning on continuing this activity, etc.
Definitely explain the organization! If they don't understand what the organization is about, it's difficult for them to gage why you got involved/why you did what you did in the organization/etc.
Maybe your pre-health advisor if you could give her a list of contacts for all your shadowing experiences? Or if you're close to one of the physicians you shadowed, list him/her as the main contact, and provide him with contacts for everyone you shadowed (maybe an e-mail for the person you shadowed abroad).
For your ENT experience (I shadowed an ENT too for quite a chunk of hours and thought it was awesome--plenty to see and learn), I would just go with the 350 hours. Good to be truthful. As for your description, I think that's a good start! Explain what you did/saw while shadowing, why it was significant, why you shadowed the doctor for that many hours possibly? (I suggested these since if you're listing the shadowing experiences separately, then that means you have a whole 700 characters to fill if you need them.) 350 hours is no small feat.
Fizzlin, thanks for the feedback. t was truly an estimation, I shadowed the guy for almost 10-12 months, and many surgeries. I settled at 300. I did not list it as my most memorable though, I listed cooking and baking with my kids as most significant, emergency room shadowing as most significant and attending a problem based learning session for a week at medical school with medical students as most significant.