You have to match it against Proteus time. You can't match it against computer time. It just won't match. Simulation doesn't occur in real time. Basically, to simulate 60 seconds, Proteus takes between 70-75 seconds.
All but the very simplest circuits will run slower than real time. So, there will always be a difference between Proteus time and computer time. For simulation, you must use Proteus time. Make it on hardware instead of simulation and you'll see that it's fine.