There's a style called .wy-nav-content that is causing the Assembly explanations table to truncate at 800px, so you can't read the function blurbs unless you go into the browser debugger and turn off the max-width: 800px style attribute:

http://solidity.readthedocs.io/en/v0.4.21/assembly.html

However, even with that attribute turned off, the really long explanations still truncate. It would be better to adjust the styles on that page so the function explanation text wraps and doesn't get hidden if it overflows.