"Realistic" function in Programable device simulator

I have a doubt about the behavior of the "realistic" instruction in the device simulator.

The syntax is:
realistic(setPoint, proportion, integral, derivative, repeat)

I understand the setPoint and repeat parameters, but, since I am not a PLC / Control guy I don't understand the Proportion, Integral and Derivative parameters.

I know there is a big therory behind those concepts, but I'd like to know if there are some general rules, or pointers, something like:

  • X controls the variability or amplitude,
  • Y controls the frecuency,
  • Don't use a value greater than A for parameter B

Thank you