That bar is used to control the simulation time and not the real time.
In the picture provded it is running at 43200x real time, so for every real second the simulation is attempting to do 43200 seconds. It is likely too fast so instead it will run as quickly as it can to get close to that value (and of course will vary depending on your computer).
If you uncheck the 'Real Time' checkbox, it will then be in simulation time more instead where you can use the slider but cannot enter in a number. The slider represents how quickly the model will run and uses the values 1% to 100%, where 100% is as fast as possible.
The difference between the 2 modes is how it handles the time between the code being ran, in real time it will wait to ensure that the viewer can keep track of the flow in a linear process, while in simulation time it is skipped compleatly and event after event will be ran with the model's graphics being updated along the way.
Firstly,thanks for you feedback !I understnad your words.howerver,eventhough i dont check the 'Real Time' checkbox, the slider bar is unavailable,it cannot move,so that the model ends in a shot time ,I want to watch the process through slowing down the slider.