keychron_qmk_firmware/keyboards/9key/keymaps/default/keymap.c

#include QMK_KEYBOARD_H

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {

/* LAYER 0
 * ,-----------------------.
 * |   1   |   2   |   3   |
 * |-------+-------+-------|
 * |   4   | 5/ENT |   6   | Dbl Tap 5 for Enter
 * |-------+-------+-------|
 * |  7/0  |   8   | 9/FN  | 7/0 = Dbl Tap 7 for 0  -  9/FN = Hold 9 for FN
 * `-----------------------'
 */
[0] = LAYOUT(
  KC_1,       KC_2,      KC_3,
  KC_4,       KC_5,      KC_6,
  KC_7,       KC_8,      LT(1, KC_9)
),

/* LAYER 1
 * ,-----------------------.
 * |  ESC  |   +   |   -   |
 * |-------+-------+-------|
 * |  BSPC |   *   |   /   |
 * |-------+-------+-------|
 * |  00   |   .   |       |
 * `-----------------------'
 */
[1] = LAYOUT(
  KC_ESC,   KC_PLUS, KC_MINS,
  KC_ENTER, KC_ASTR, KC_SLSH,
  KC_0,     KC_DOT,  KC_TRNS
)

};