iirc
subjects are broken into units
adv is a 2 unit subject, therefore your 2 unit adv english mark is divided into 2 separate units
1 or 2 units of those adv eng 2 may not count because atar requires [your best] 2 units of english which can come from ext 1 (1 unit) + ext 2 (1 unit)
but only if you have 11+ units and it's your worst subject