Generally scaling doesn't usually occur for subjects, so make sure you don't drop any 'easy' marks during the semester (such as forgetting to do a weekly quiz), but I have had some subjects which I knew were definitely scaled up when I did them (such as Principles of Finance and Calc 1), though that decision is based on the subject coordinator (I have done subjects which had unexpectedly difficult exams but no scaling).
As a three year in biomed, for the most a H1 is a raw mark over 80, and defs a H1 wam is achievable, but it does take alot of work. Pretty the only subject in Biomed that had scaling was Chem for Biomed and the Maths subjects (for certain assessments) but this was back in 2019, with all online assessments (i.e. final exams being online) I am not sure how the scaling was in 2020.
But yes a mark of 80 does not put you in the top 20%, it is just your raw mark.
Best of luck with first year!
Feel free to pm me if you have any question about first-year biomedicine I would be glad to help