There's an additional square pad underneath where the R9 resistor is supposed to go... what's it for?? I don't want to put a resistor over it and block it if I need to use it for something... Thanks!
It's a via. It's how top and bottom traces can be connected when there is no component (used when you run out of ways to route traces).
No need to do anything there.
Good to know! Thanks, Brian.