I understand, I had the same problem initially.
If you like, this weekend, I'll try to take one of my maps, and show, effect by effect, what happens when I vary the parameters.
You should know, and it is very important that the level of variation depends on the size of the map: a large map, it will take a varying values to change a little effect (for example from 25 to 50), whereas in a small map, it will be very little variation of value (eg 1.5 to 2.5).