Number lock doesn't work on 9300. Why?

That makes no sense at all.  If you look at the key, 'num lock' is white and 'scroll lock' is blue on the same key.  Function key is blue and corresponds to blue 'scroll lock.'  Besides, if I push num lock, as directed by the owner's manuel, the lock should occur without the function key.  Also, if I push the num lock key, the light with the 9 in it comes on, as if it is locked, yet it does not work.

try to go to the BIOS and see whether the same thing happens. if it does, most likely it is the keyboard. on some occassions a simple reseating of the keyboard will do. if not, then it is up for replacement

I noticed the same symptom you described (I just bought a new i9300 too) so I did some testing and think I got it to work.

If I turn on the "numlocks" (just tap the Num Lk button) and then while holding down the Fn key, I do get the numbers such as 4 in place of the U key etc.

It is a bit confusing but at least it does work (for me anyway).

Good luck!