reading 36 question 3- cash and carry storage cost

In Q3, reading 36: storage cost = 0.05 per month effective interest rate per month = 1% spot = $2.5 F = $2.6 theoretical F = $2.7273 we do a synthetic short position (long forward, short spot) to do an arbitrage. i was reading the solution and realize that you get the storage cost paid to you. why is that?