0xFFFF. Within your
keymap.cit may look like you have functions and other special cases, but ultimately the C preprocessor will translate those into a single 4 byte integer. QMK has reserved
0x00FFfor standard keycodes. These are keycodes such as
KC_LCTL, which are basic keys defined in the USB HID specification.
0xFFFFwhich are used to implement advanced quantum features. If you define your own custom keycodes they will be put into this range as well.