UNCLOS determines that and as UNCLOS has been implemented, there has been a backlog of dispute resolution, plus the date of each nations claims are determined by when they signed the treaty, so resolution can't begin until all the overlapping claims are made.
You may recall China and Japan in a recent hot dispute over this same issue, but they reached an temporary resolution until UNCLOS can finally make the determination.
At the same time these various nations are in dispute over who it belongs to, there have been confrontations between China and US Navy vessels who are mapping the floor/shelf in that area because the US says it doesn't belong to any of them, it is international and under control of UNCLOS.
Same situation in the Arctic Ocean. Russia, Canada, and Denmark(Greenland) have overlapping claims on the Lomonosov Ridge and the US says it doesn't belong to any of them, it is international.
test
second test