Why is there a difference between the number of devices connected depending on if I'm looking at my team? I'll go home in the app or to display on my t mobile home internet gateway

When trying to view the number of devices connected to our home internet gateway, the numbers seem to differ depending on whether you're looking at the app or if physical gateway itself. The physical gateway always shows one extra device connected that is not listed on the home. Internet app. Is there a reason for this?