This compression system is a very handy invention, especially for Web users, because it lets you reduce the overall number of bits and bytes in a file so it can be transmitted faster over slower Internet connections, or take up less space on a disk.
Concrete hardens to 600PSI (Minimum) after 24 hours. This means that 5 three grown men could all stand on a pogo stick (if that were possible) who's base covers 1 square inch without harming the concrete. You walking with shoes on exert about 10 PSI, well below anything that could damage the new pour.
Drying time is about 6 hours, at minimum (meaning no one should be allowed to walk on the patio during this time). But wait 24 hours before driving a car onto your patio. Temperature is a factor in the curing (drying) process. The colder it is outside, the longer it will take for the concrete to dry. Rain is your enemy in this project.