Yes, unit entitlements can change, but it’s not something you can change alone.
All you can do is start the process, independent valuer then calculates the new unit entitlements followed by NCAT reviewing and deciding if they should’ve registered.
Yes they can be backdated, but it requires a seperate order from NCAT.
Be careful, changing unit entitlements can bring about some surprising results for some people, after all levies are calculated on market value at a common date.