The quorum is about turnout, not the result. The law sets no general quorum for a VvE: decisions are taken by an absolute majority of the votes cast, unless the articles provide otherwise (article 5:127(1) BW). A quorum therefore comes from your regulations.
Under the Model Regulations 2017, ordinary decisions have no separate quorum. For heavier decisions (article 56.5), at least two thirds of the total number of votes must be present or represented. If that is not reached, a second meeting follows where turnout no longer matters (article 56.6).
Proxies count: what matters is votes present or represented. Under the Model Regulations 2017, the attendance list is decisive for the quorum (article 50.3). Older regulations may have different quorum rules.
See also: Absolute (simple) majority, Qualified majority, Second meeting, Attendance list (presentielijst), Proxy (volmacht)
Read more: Quorum and majorities in a VvE
Legal basis: Boek 5 BW, art. 5:127, Modelreglement 2017, art. 50.3, 56.5, 56.6