According to the Horizontal Property Law, the resolutions of the Meeting of Owners are passed by a double majority, that of owners and that of quotas. For the first majority, the number of owners in favour or against the resolution are counted and you need more than one half in favour for the resolution to pass. For the second majority, the amount of quotas in favour or against the resolution are counted and you need more than one half in favour for the resolution to pass.
For the first majority, if a property is owned by more than one person, these owners will have to decide which of them casts the vote as that property will only give one vote. Likewise, if an owner owns more than one property in the community, this owner will only have one vote for the first majority.
For the second majority, the quotas of those owners voting in favour or against are added up. If an owner owns more than one property, his total quotas of all properties will be taken into consideration.
That is the Law and cannot be modified by the Statutes or internal resolutions.
A different thing is how the owners' contribution to expenses is calculated. According to the Law, the contribution will be based on the quotas each owner has although the Statutes can stipulate that the contribution will be the same for each property, regardless of the quota. This resolution to alter the way expenses are distributed requires unanimous consent and to modify it in the future, a unanimous vote is also required.
Since the way it is being done in your community required an express change from the quota based system to an equal contribution by all properties, I would try to make sure this was correctly voted in when it was first introduced. If it was, you can ask that the next Meeting of Owners (whether AGM or EGM) discusses changing the way expenses are distributed to a quota based system. As mentioned, to pass, the resolution requires a unanimous vote. This is quite difficult to obtain because generally those owners that will have to contribute more in a quota based system will object.
To summarise, you can change the way community expenses are distributed among the owners but you cannot modify the way votes are computed in Owners Meetings.