Hey kitty_kate, first of all welcome
That rule means you won't get listed on some LLs if you put recips of other LLs that usually contain 3 links.
Check out for example GG's recips here:
http://www.link-o-rama.com/greenguy/linkstuff.htm ( All recips contain 2 links, that's why you won't get listed if on your free sites submitted to LOR for example you put recips that contain 3 links ).