You shouldn't be worrying over trivial things like the break time and the exact procedure and stuff. Just stay calm and be yourself. Take deep breathes and release all the air from the lungs in a quick whiff. Repeat it four to five times and you'll feel relaxed naturally.
So here comes the actual part. Only after you click "Yes" does the break timer start. And then, you have to raise your hand and a person will come to your desk and escort you out of the test-zone. Then you'd have to do your thumb and palm prints again and then, your break starts. When you report back to the test-zone, everything above starts with frisking you, if need be, to check if you do not carry anything illegal into the test-zone and then the palm and thumb prints will resume. Meantime, just make sure, you take a good leak, drink some energy fluids, have some protein bars or something and most importantly, DO NOT PONDER over the last section, all within a stipulated 5 mins, leave a gracious 3 mins to the security routine.