Although the numeric keypad has the same numbers on them, as the letters, the keyboard mapping returns different keycodes for those keys. For example, the Enter key on the keypad is not the same as the Enter key on the keyboard. Some programs take advantage of this fact and have different behaviors for these keys and some are programmed to behave in the same manner as there corresponding character. It would appear that XL is not programmed to treat the keypad numbers the same as the numbers above the letters, when it comes to the keyboard shortcuts.
In other words, there is a shortcut for CTRL-1 not CTRL-Keypad 1