Sorry guys, I only know this much from my own experience with the NX30:
1. Each slow mo shot is a fixed 3 seconds of action (real time) . No longer no shorter.
2. Recording starts the moment I hit the record button even though the camera says: Buffering. No need to hit stop.
3. It takes 18 seconds from the time you hit record to the time the camera is ready is to record the next shot.
4. The clip is 12 sec long straight out of the camera.
So by deduction: 12/3 x 25fps = 100fps