You may see entries in your Device List that consist of a string of numbers and/or letters. This may happen for devices that do not send identifying information to the router when they join the network. Typically, the string of numbers and/or letters displayed in the Apex Managed WiFi app are the hardware address (also known as the MAC address) of the device. The MAC address is typically found on a sticker on the device or, if the device has a management interface, somewhere in the network settings.
To properly identify the device, compare the device MAC address to the string of numbers/letters listed in the Apex Managed WiFI app.