How do I set up my iTunes Genius to play selections from all, not just some, of my songs in my currently playing playlist?

Last night, when I played my playlist songs with iTunes Genius, my iTunes, with one of my playlists selected, and set on "Shuffle On," "Genius Shuffle On, "Genius On," "Match On," and "Play," played selections from all of my songs in my playlist. Today, my iTunes Genius went back to the same problem it was giving me before last night. My iTunes Genius has been playing selections from just a few of my playlist albums. How do I set up my iTunes Genius to play selections from all, not just some, of my songs in my currently playing playlist?