my 12 yr old child set up an apple id on his new iphone 12 before I could set up screentime limits on my phone. It's not showing any activity on my phone for screen time so, how do I add him so I can see his activity?

My 12 yr old child set up an apple id on his new iphone 12 before I could set up screen time limits on my phone. (he hadn't finished setting up his profile with the correct birthdate, which cannot be changed at this point) I'm unable to view his activity from my phone but, the limits are set on my phone as well as his. There's no way for him to ask me for more time because for some reason, we're not synced together. How do I do that? Does he need to set up a different apple id now?