The MSW routine is run as a separate thread. The plotting is also its own thread. Unless you have a multiprocessor mahcine, the threads are not run concurrently. However, this provides the essential benefit of seeing how the integration proceeds, until all about 144 runs have been computed. Often the first points are enough to give an image what is going on.
Later points add accuracy.
Sometimed the solar screen is not updated regularly. To force the update, repress the solar neutrino button, or minimize and maximize the browser window, or do something similar, depenping on the platform. The finite size of the neutrino production region is accounted for by taking an average of 17 different initial points. Angular distribution is still incomplete. For the Sun and the solar neutrinos the models and data by John Bahcall is used.