Aquarian – I think we may be at cross purposes here, in that there are two (2) scenarios where a change may be made to the schedule of unit entitlements in the situation that you describe, and where both require in the first instance a general resolution (i.e. passed by a simple majority) of Owners at a General Meeting to engage the services of a Registered Valuer to review those.
The first can occur at any time within two (2) years of a Plan being Registered, where under the provisions of the NSW Strata Schemes (Freehold) Development Act (1973) the passing of a Special Resolution is all that’s necessary for an application to then be made directly to NSW Land & Property Information to change a Plan’s Schedule of Unit Entitlements.
The second can occur at any time after the two (2) year period (above) where then (i.e. after the Valuer’s review) on the basis of either a general resolution (simply majority) passed at a General Meeting or a grievance by the minority of Owners to which your post refers if that resolution didn’t pass, an application can be made to the Strata Division of the NSW Consumer, Trader, and Tenancy Tribunal (CTTT) under Sect 183 of the NSW Strata Schemes Management Act (1996) for Orders to reallocate Units of Entitlement under the process described by Jimmy.
Hopefully that answers your question about the nature of the Resolution required; special up to two (2) years from Registration and simple thereafter.
If only your Owners Corporation had passed a general resolution to engage the Valuer when it first met two (2) years ago, it would have complied with the first scenario that I outlined and could have avoided the CTTT altogether.
Finally with regard to Sect 183(4), it’s likely one of those quirks that the CTTT thrives upon, but I think it’s referring to the original valuation that was produced when the Plan was Registered, so the Member can compare that with the one now done to support the requested reallocation.