The "f(r,t,z)" window shows a wireframe section of a cylindrical domain colored according to the value of the function.  Clicking the "Surface" checkbox places a surface over the wireframe again colored according to the value of the function.

The "T-Slices" window shows slices for various values of t according to the value of the function.

The "tmax" variable will increase the amount of the wireframe domain displayed as well as the number of T-Slices.

The readout "M" gives the mass of the section of cylindrical wireframe displayed, so varies according to the selected value of tmax.