Is it a set number, or do you need a number of credits? Do people all do the same number of courses?
10 units are required to obtain a HSC. A minimum of 2 units of English are required. Most subjects are worth 2 units, with some extension subjects being worth 1. Students often choose to study more than 10 units as insurance for slip ups. Only your best 10 units are counted (2 units of english must be counted).