You can use a jumper wire. Any low value resistor will do. Means nothing for burn-in purposes.
I admit, the instructions are confusing in this area as both boards have an R1, etc. When I build the Pro, I install both resistors so I don't have to think. Then I can wire up either input. I use my assembly and soldering moments as my 'down' time, where I don't have to think. It just becomes automatic after a while. I can veg out and recover from intense layout or design sessions.
jh