This workout is done for time. No designated rest intervals, though I have found breaking it up into five repetition sets with a tabata style rest interval works well. Five repetitions takes me roughly 20 seconds, with 25 to 30 seconds rest before the next set. Optimally, I should be looking to achieve 20 seconds work versus 10 seconds rest; this will see an overall time under 5 minutes. This is fairly realistic given 50 burpees can be achieved in 2 and a half minutes without stopping.
If this is too easy, then simply increase the volume to 100 burpees instead of 50.