You have your subjects
Say they are
Maths 2U
MX 1
English 2u
Legal 2u
Physics 2u
Biology 2u
So you have 5 2Unit courses and 1 1unit course.
Remember Each Unit is marked out of 50.
For example
These are your marks per unit of work (remember each unit is worth 50)
MX 1 (45)
Biology (34)
Maths (50)
English (50)
Legal (50)
Physics (50)
This means 2u maths, legal, physics, and english will all count as a whole (Basically if you have a 2U subject when it is marked, remember it is out of 50, it will just double)
For your final 2 units needed to make ten you have bio and maths extension. This means That means one unit will come from biology and one unit from your extension because they are your lowest marks to form your 10 units