So parking at work today with front of the car facing the parking lot road, I got 10 incidents in about 10 hours. I lost 11 miles while parked. My 16 GB USB Drive (actual usable 14.2 GB) was over 11 GB full. The recentClips folder contains 177 of 1 minute files (front, left, right). I think it is supposed to be 180 (3 x 60 min) but somehow 1 min (3 files) are missing. The savedClips folder contains 10 folders (10 incidents). Total size is 6GB. It is not 10GB because some of those incidents happened within 10 min of each others so some incidents have less files. All of them were people walk past the front of my car. The last incident was me coming back to the car (on the left camera). So if you activated Sentry Mode, you are going to have at least 1 incident saved (about 1 GB) of yourself coming back to the car. Unless you disable Sentry Mode on the phone first.
When it detects an incident (someone walked within 2 feet of your front or side), It saved that min of video and the previous 10 minutes. The incident usually occurs in the newest full 1 min files (set of 3) within the incident folder.