It probably is over 100%. That’s unusually high but 100% short interest is not some sort of special number. Shorting works by borrowing a share and selling it to someone else. There’s no reason the same share could not be borrowed multiple times, as the shares are all fungible.
From what I understand, it is a slightly special number. Each one of those shorts is supposed to have some kind of contract in place that can be used to cover the position (e.g. a call option that would ensure that the stock could be purchased, even if the options contract isn't ITM). If there's over 100% short interest, then it's impossible for all of the outstanding shorts to be covered in that way (or, alternatively, the contracts to cover the short positions are naked, not the shorts themselves).
I'm by no means a finance guy and if I've misunderstood this, I'm happy to be corrected.
(Disclaimer: my expertise on the stock market extends to knowing how to spell "stonks".)
I posted a chain analogy elsewhere[0]. My understanding is that short interest being > 100% just means that the average length of the "short-lend" chain is greater than 1 "short-lend" pair. I don't think that such a chain is anything special - just that getting rid of the earlier short in the chain requires getting rid of the latter short in the chain first.
That doesn't matter because nobody covers the stock at the same time. The shorts buy back a few stocks, return it, then a bit later buy it back again from someone else who sees the higher price and decides to cash out. Neither of the two owners above knows that that they both technically owned the exact same stock.
Most stocks are head by the broker who combines them all into one listing of total number of stocks owned. This is all electronic, nobody ever worries about the actual stock behind it. When the company sends out a shareholder mailing they just give the company all the addresses, not how many shares anyone has. (I'm not sure how voting is handled!)
Note that there is a loophole above. It is possible to get the physical stocks personally instead of letting your broker handle it. This can force a short squeeze as your broker will be forced to unwind everything far enough to find real shares for you, and if required will force one of the shorts to buy back shares on the market. This has happened a few times in history, but few people have the means or inclination to pull it off (and it isn't what is happening here).
Sure, but when you short, you owe a share. If more people owe shares than there are shares for sale, you have a serious supply and demand problem depending on when those debts come due. If shorts are significantly over 100% of float, then it would seem that they are still vulnerable to further squeezing.
Further shorting is completely possible - nothing stops shares continuing to be lent, but doing so just makes the likely supply shortfall worse.
The supply of shares for covering is not constrained by the number of actual shares in issue in the ordinary course of trading (you can create this condition artificially if you want to but people usually don't). There can always be more shares created for short sellers to cover with through shorting itself.
Short squeezes are usually not about supply constraints, they are about forced buying caused by margin requirements. High short interest just indicates a lot of potential forced buyers in the event of a price spike. Except in special cases there is particular magic to having 100% of the float on loan except that this is a high number which suggests many potential forced buyers under the right circumstances.