The rep scheme is descending, which lets you target both strength and condition during the workout. You'll perform each movement for 10 reps. Once all of the exercises are completed, you then perform each movement with 9 reps, and so on down to 1 rep of each movement.
So you'll do 10 deadlifts, 10 pushups, 10 squats, 10 pullups, and then move on to 9/9/9/9, etc.
If needed, you can scale down the weight for the deadlifts & squats. But keep it at a weight that's challenging for you. After all, it is the countdown reps CHALLENGE!