The simulation speed (or the simulation ratio) is how fast RoboDK simulates a real motion. A simulation ratio of 1 means that a movement that takes 1 second on a real robot will take 1 second to simulate.
RoboDK simulates 5 times faster than real time by default. That means that a program that takes 5 seconds to execute on the real robot it will be simulated in 1 second. Speeding up the simulation increases this ratio to 100. Normal and fast simulation speeds can be changed in the Tools➔Options➔Motion menu.