That can only happen with naked shorting, which is (illegal and) not implied by >100% short interest.
Some of the short sales refer to the same shares; say there's one share in the company and it's (borrowed and) sold short thrice. The company's one share has been sold three times, but there haven't been sales of more shares than there are in the company - the three (short) sellers need to get that (same) one share back to close their position in sequence.
Some of the short sales refer to the same shares; say there's one share in the company and it's (borrowed and) sold short thrice. The company's one share has been sold three times, but there haven't been sales of more shares than there are in the company - the three (short) sellers need to get that (same) one share back to close their position in sequence.