Yout pretty much on the mark, Peter.
It’s 75 percent of those voting at a general meeting as calculated by unit entitlements (special resolutions always have to be conducted according to UEs).
The 75 percent is the required proportion of the vote, not of those in attendance and certainly not of the total owners. Abstentions don’t count as votes.
So, for example, in a building of 100 units where 60 owners turn up who are elligible to vote (i.e. they have paid their levies) and they all have equal UEs (which is never the case) and 44 of them vote yes and 16 vote no, the motion fails.
But if 44 vote yes and 13 vote no and one abstains, the vote carries. It’s complicated.
Critically, for the original poster, items that require a special resolution have to be shown as such on the agenda issued two weeks before the meeting or the vote doesn’t count. It’s up to the chairman or secretary (advised by the strata manager) to make sure that motions requiring special resolutions are properly signified.