Kyanar:
It gets even more interesting - SEC filings seem to indicate that institutions (Vanguard, BlackRock, pension funds, etc) may own 162% of the company!
GME Institutional Ownership - GameStop Corp. Stock (fintel.io)
If this is not a miscalculation (it doesn't appear so - the last annual report said there was 87m shares of stock on issue, and no sign of a share issue in that timeline) then something very illegal has occurred, and since the float is then a negative number - the stock interest may be even worse than originally thought!
Is it illegal though? (assuming that it's true).
You contract to "borrow" a share when shorting that confers most (if not practically all) rights.
You lend that share to someone else. That's "two shares" counted as shorted - even though it's only the one share.
It's incredibly stupid and irresponsible greedy behaviour, but may not be illegal if you can cover the risk some way (even if it should be - the regulators need to look at "shorting" stock in companies in trouble - at best it accelerates their demise).