How do PR sets work?

A PR (personal record) set will have a target number of reps. The goal is to hit as many reps as possible with the reps listed being the minimum. After you perform the set update the reps field with the number of reps you completed and check off the set. If you hit over the target the app will automatically increase your Training Max for that exercise. If you hit below the target, you can optionally choose to mark the set as 'failed'.