What's the earliest time the CW office allows people to go inside and wait for them to open? Last time (2 years ago) I was there at 8 in the morning and there were already people waiting in line inside.

I'm on 60 tourist visa and going for the first extension soon. I have a walking hard cast on my leg for a (not serious) broken ankle and I'm worried that they might think I'd want an extension for medical reasons which is not the case at all. I have my flights back home booked for next month and I can show them my itinerary. Will they ask for a medical certificate just because they see my leg cast?