“You cannot make an arbitrage profit with delta hedging.  Arbitrage is, by definition, risk-free.  Delta hedging is not risk-free.” 

This was posted by one of the forum editors last year, just to make sure schweser example on pg 180 that exactly does that is incorrect, right? 

What does the formula below mean? 

-HS0 +C0= (-HS down + C down) ÷ (1+rf)