Hello Monpon9,
Welcome to Apple Support Communities!
Let's ensure that you have Block at End of Limit enabled.
If your child is still using an app after the limit is reached then you need to enable Block at End of Limit. If this setting is not enabled, your child will be able to ignore the app limit suggestion.
Go to Settings>Screen Time>Family>Your Child's Name.
Select an individual app or app category and tap NEXT.
Enable Block at End of Limit.
We also want to provide you with the article for setting up parental controls to ensure that they are set to how you need them to be set.
Use parental controls on your child's iPhone, iPad, and iPod touch
Let us know if you have any questions.
Thank you for using Apple Support Communities.
Take care!