not only is this probability table incredibly wrong (in paper you are 3/10 to get 6 mana on the first goblin and virtually guaranteed to get 5) but it's also a weird ETB trigger? So, 1) you don't know how much mana it's generating before you play it and 2) your opponent can't respond by removing the creature in response to the trigger to deny the mana generation.
why even bother putting this card on the platform????
Also strictly worse because there's NO option to get Mind Goblin (1 red mana)