Your best 10 units (and at least 2 units of English must be included) are used for your ATAR and are weighted by the unit value contribution to those best 10 units.
For example, suppose you have five 2 unit courses and a 1 unit course. Your worst (non-English) subject is a 2 unit course. Your best 10 units are your four other 2 unit courses + 1 unit course + 1 unit from your worst subject.