reread my post, it's edited while you were posting
And to add to it:
Fn is not a shift state key like CTRL, ALT or SHIFT.
Fn is a toggle key which maps other keycodes to the keys.
You first press
Fn to toggle some keys on your keyboard (just like CAPS LOCK, or NUM LOCK does on a normal keyboard). In other words
Fn is not part of the final keycode.
/ 
