HTML Version : This shows the version od coding you used in the design of your site.
HTML content can be minified and compressed by a website’s server.
Size : Shows the size of the HTML used on your site.
Compressed Size : This is the size of the HTML on your site once it has been compressed.
The most efficient way is to compress content using GZIP which reduces data amount travelling through the network between server and browser.
This page needs HTML code to be minified as it can gain 8.1 k B, which is 13% of the original size.