As you say the audit opinion reports on individual matters – not an aggregate.
An answer may make passing reference an aggregate – e.g. if a matter you have been asked to consider is not individually material, adjusting for it would reduce the aggregate of the otherwise uncorrected misstatements. Specimen Q2(b) is about uncorrected misstatements – so consideration of aggregate in (ii) is worth a mark – but you wouldn’t lose a mark for not considering it.