'Way back in the olden days, search engines only read the first so-many characters of a page. If the top of your page was filled with meta tags, scripts and other clutter, search engines left before they reached the actual content. However, this hasn't been an issue with the major search engines for many years now.
Perhaps @aijhones55 accidentally put the figures back to front and meant 25% code to 75% content? That would seem a bit more sensible, but I'd still want to see an authoritative (e.g. Google or Bing) source for such figures before I'd start worrying about them.