Circle is showing usage by a device that is off - Orbi RBR50

I'm using Orbi wifi and the Disney Circle app to manage my son's access to WIFI on his PC with a time limit and bedtime. The other day my son complained that he had not used his full 4 hour time limit when Circle said he had hit his time limit and then shut him down. He’s usually very good about disconnecting from the WIFI when not using his computer to ensure the WIFI isn’t being used and working against his time limit. So yesterday, when he got off hic PC to go walk the dog I checked his usage and it showed 1 hour 40 min. When he came back 15 minutes later I checked again and it showed 1 hour and 55 minutes of usage. So I told him he forgot to disconnect from the WIFI, and he informed me that he fully shut down his PC. And I checked, and he had. And the Circle app showed that it was still using the WIFI/internet.

The Circle profile for him has only his PC on it and I verified that the mac address on his PC matched that of the device on his profile.

So Circle is showing internet usage by a specific device while I know that device to be off and/or not connected to the WIFI.
I have zero understanding how this can be. Any ideas or help you can provide would be super helpful.

Thanks!