"40 hours" in his context here is actually a work day, so 7-8hrs.

He says "40 hours" because he feels like he's managed to do 40 hours worth of work in this time, but then has to spend another "40 hours" (actually: 1 day) just going around kicking tyres.

Obviously the implication is that it's a net gain of some kind, but he's unsure if he caught everything.

(sorry to reiterate the GP, but I feel like you missed the important nuance that it's not a real 40 hours of time).