Burried deep in the psrtutorial site under "Resources" are some Music Tips. One of those "lessons" is an article I wrote on Counting Out Loud. It shows you how to handle those eight notes as well as the dotted eight notes and sixteenth notes. Here is a direct link:
http://psrtutorial.com/Resources/R_MusicTips/MT_Counting/mt_counting.html

Also, under Resources, is a section called Music Links. It provides links to many other "tutorial" type sites that deal with music theory, as opposed to figuring out how to get the most out of the PSR. Here is a direct link to that page. You may find what your looking for there:
http://psrtutorial.com/Resources/R_MusicLessons/r_musiclessons.html