The standard keyboard HID descriptor has room for only 6 keys (plus the 8 modifiers). In principle the keyboard can just define a larger descriptor, but not all

The standard keyboard HID descriptor has room for only 6 keys (plus the 8 modifiers). In principle the keyboard can just define a larger descriptor, but not all hosts allow this. Some 'NKRO' keyboards pretend to be a hub with multiple keyboards attached, but at least some of these don't handle modifiers properly for hosts that don't merge all keyboard input into one.