I have an Archer VR1600v Modem

I have a question related to the parental control in this modem.

I have followed the manuel instructions in parental control setup. For example, I would like to restrict my children's device to access youtube.com from 10pm every night. 

If my children try to log into the Youtube after 10pm, they can't.

However, if my children are already watching a video on youtube at 955pm and they can still continue to watch the same video even after 10pm. Why would it be?

Does anyone know if I could configure the modem so that the websites (Youtube or other online games) would be terminated at 10pm immediatley even though the internet for this website has been already established before 10pm?