You do realize the block does not reflect a "rolling" aggregate? It is simply based upon shares held in particular accounts that can be margined, often financiers who allow borrows against their position or a portion of that position to make some additional money. The reason you see less is because those people have eventually been allowed to sell their shares into the market. It is just another way to hedge against losses over time while waiting for conversion to free trading for example.
Daily Reg SHO is meaningless in a market in which it is mostly based upon Riskless Principal. The percentage is useless especially in such illiquid securities like this where it can be 100% each and every day and still have nothing to do an actual short position or FTD.
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