They’re referring (I believe) to the screenshot right at the top of the article, which includes this absurd calculation:

border-radius: max (0px, min(8px, calc( (100vw - 4px - 100%) * 9999)) );

My guess (hope!) is that this is not ‘serious’ code, but padding for the sake of a screenshot to demonstrate that it’s possible to use each of these different features (not that you should!).

Don’t even need to remote in to anything, just store your working code on a network share