I'm guessing the trials were weighted ~40%? So considering the fact that a 40% weighted task wouldn't lead to a drop as severe as 90+% -> 20% total internal mark, I would doubt that its unbelievably impacted your overall HSC mark. Even so, the drop from 2nd to 16th would suggest those ranks are competitive or you bombed the exam, either way 16th is most definitely not the end of the world and a comfortable HSC exam mark would account for the lower moderated internal mark.
