It seems that recently all info that coul be cool to have in a11y guide about Mouse Keys are disappeared.
Don’t panic. A fresh new wiki page is now available, providing detailed and tested info (waiting and hoping for a more more cool Mallard version of GNOME A11y Guide).
Missing stuff? Maybe a picture like this (a11y team, don’t kill me: I could like to place it directly in keyboard capplet to show a quick preview) and a video showing keypresses and results (do you know that Mallard supports video? no?)