The goal is to perform the entire challenge with 20 unbroken sets. If you must rest, do so and complete the set.
You'll notice this always equals 11 reps total per superset. So that's 55 reps of each exercise and the goal is to complete it in under 20 minutes. If you're unable to complete it in 20 minutes, stop and record your total number of reps and get back to training.
If you haven't been doing bench press or chin-ups, get proficient in the lifts until you can perform multiple sets of 10 of each. Until then, either skip this challenge, pick easier versions of the exercises, or start at a lower rep range. Have a spotter present on the bench press at all times.