The claims floor asks how much bitcoin is owned not as coins under the owner's keys but through a claim on a company, a fund or a state that holds the keys. The desk adds each holder's latest disclosure, in bitcoin, from the holder's own filing or record, and divides the sum by issued supply at one pinned block.
It is a floor in two senses. Only disclosed positions count, so the amount held through claims is higher than the figure. And every part is cut, never rounded up, so the printed figure never exceeds its evidence.
Each disclosure keeps its own date. The block pins the denominator only; it does not mean every holder held its amount at that block.