Assuming the Plan number starts with a SP or RP, your property is a strata plan. This means the common property is all the land on the plan excluding the footprint of each unit or accessory unit which is defined by buildings.
Being strata the horizontal boundary will be stated on the legend which typically will be “lies within floor/ceiling” or it will state a height and depth “25 feet above” or “3 feet below”. The vertical boundary will be median, unless otherwise stated.
So what does that mean to you.
Most likely the areas you refer to as exclusive use are common property. In Victoria we don’t have exclusive use bylaws, but the OC has the power to lease or licence any part of common property by special resolution.
I would suggest that your OC revisit all previous approvals and acknowledge those approvals and formalise the future management of those areas by granting lease or licence to individual owners.
The upside, a proper lease/licence covers all the assumptions like maintenance, repair, replacement, improvements, any limitations of use, insurance. These are the topics that lead to most disputes so good to have clarity.
The downside, if you are the only one with an area like this, the cost of preparing the lease/licence will be your cost. If there are others in same situation but not all, the cost will be shared by those needing the lease/licence.