Every time you click the flag it will run a experimental simulation on dice rolls. The higher the number of tries the more accurate it gets. The whole variable situation describes in a set number of dice rolls how many are divisible by 2, 3, or 4, etc. D1, D2, D3, D4, D5, and D6 stand for division 1, division 2, etc.
Note that to change the number of tries go into the project and change tries to any number you wish. Also if you set the number too high even with run without screen refresh it will take time to load to check if it is done just look at D1