Hi Freddy
I know bog all about HSC but I do know about assessing evidence.
The way to go about this is to take your evidence, assess it against the main unit it refers to and then work through all the other units you are doing to check if there are any PC's or knowledge the evidence covers. For instance, I assess customer service where one piece of evidence can cover all eight units.
You need to especially look at the mandatory units when doing this.
Don't worry, it's taken me five years to get to the stage of looking at a piece of evidence and rattling off which unit it covers.
It takes a bit of time but it's worth it.

Dave