I have been testing Windows 10 parental controls and they simply don’t work. Many others have this experience.
They simply do not reliably impose screen time limits and in some cases do not even successfully filter porn. A limitation (not a bug) is that filtering only works with IE and Edge so you must prevent your child installing Firefox or Chrome.
Although it is necessary to set up Microsoft Family and add your children to it I advise that you do not use Parental Controls but invest in an alternative solution.
— update 2016/10/27 —
I found on one machine the Settings said that “cannot connect to Microsoft Family”. It seems that it fails dangerous and just lets the child login with no controls. It is possible that this was the root cause of the lack of screen time controls.