Games : Randomness of Goblin Blastmage

For Goblin Blastmage I recognized that the blasts are not quite so random. I have enough data to know it is not completely random, like Mad Bomber. Blastmage seems to prioritize the first unit it hit with a blast instead of randomly splitting the blasts. It does sometime split the blast randomly but not even near to how much it should do that.

I am guessing it works something like this:

setInitialTarget()

for 0 to 3 {
  randomNumber = somethingBetween(0, 100)
  if randomNumber < 80 
      blastInitialTarget()
  else
      blastRandomTarget()
}

I would like to learn how exactly the randomness of Goblin Blastmage works?