I'm pretty sure that at level 4 a DC 30 check is going to be an auto-fail even rolling a Natural 20. ... Yeah, you got a 25 with a +5 modifier. I guess you're just rolling the dice to check the rolls generated?
The boxes with a double underline are the averages it took to get to the final success #, which is right before it. The green highlight for the 20 was a natural 20, where I succeed ^.^