Screen time limit not working

I have screen time limits set up for my kids phones, but the limits continue to be exceeded. I’ve asked them over and over how they’re doing this, and they are just as confused as I am. For example, I set a 2hr limit for one app, which should equal a weekly limit of 14 hrs. Yet, they hit just over 15.5 hours. How is that possible? These parental controls are in place to help parents, but they’re not working.