your external mark will still be whatever you get in the HSC, your internal mark, say you're 10th, would be whatever the 10th highest mark someone in your cohort gets. This is a simplification of what they actually do (Cause they look at how your internal marks were distributed, etc) but it...
forgetting that L tends to be an asian dense last name, so i would thing that the L might be slightly more dense with band sixes especially for chem and phys