Hello. It would be my pleasure to assist you with this. Please see below :
In the Devices section, you can view all devices that are currently or were previously connected to your home network, as well as devices that have WiFi access currently paused.
When a device first connects to your home network, the default name of the device, which is either the manufacturer-set name (i.e., hostname or MAC address) or the one you gave your device when you first set it up, will be displayed. Devices connected to the public Xfinity WiFi hotspot, xfinitywifi, will not appear in your Devices list; hotspots are separate from your personal home network.
If you do not recognize a device:
For a more detailed explanation, please visit : https://www.xfinity.com/support/articles/personalize-customize-hnetwork-xfi