Earlier quoted context omitted.
Then you are not paying attention. The floating shares are fewer than the shorted shares. Even if all the floating shares were bought, there are not enough shares to cover the short's position.
So what? The same share can be bought more than once in just the same way it can be sold more than once; in fact, the one necessarily entails the other.
We saw this happen in 2008 with Volkswagen. 1% of the total shares were floating because Porché had purchased the remaining, the rest of the shares were owned by institutions and they were not selling them.