As you might have noticed, the percentages you're repping out for the strength portion of your workouts are climbing. That's intentional. This program won't just leave you lean and chiseled; it'll help you develop functional strength as well.
Because you're lifting more weight, I'm increasing the rest periods between sets. In order to lift well through every rep, you need to make sure you're recovered before you get back under the bar. After every set, sit down, drink some water, and relax. If somebody needs to work in, let her!
Don't forget to write down your back squat weight, your circuit times, what weights you used, and how you felt after finishing the workout.