Page 2 shows the pharmacokinetic model for this simulation (also available by clicking on the option at the bottom left called "Pharmacokinetic Model"). The equations used are also available - click on "Equations" at the bottom left.
Page 3 provides instructions for the simulation and page 4 covers the simulation itself. In the simulation you can see how changes in the following affect plasma drug concentration levels over time:
The results can be plotted either on a linear scale or on a semilog scale.