Belle22 Remember Unit 3 contributes to a very small part of your study score, especially for maths subjects. There's no point wasting energy in worrying about unit 3 sacs, it's not gonna change anything. Give it your best for unit 4 and the exam and you'll do well.
I was in the same boat for chemistry in which i flunked unit 3 for my standards with an average of 85% and rank 5-7. I did very well for unit 4 with 100% sac average and was promoted to rank 1 overall and finished with a study score of 43. If I pondered over my unit 3 results this would not have happened.
Don't leave any regrets, just continue working and you'll get the atar you want.