Cowboy bebop-question

[whatsherface]

This may seem a little confusing so bear(sp) with me.  
I bought The Perfect Sessions dvd and it said it had episodes 1-26.  I opened it and it showed Sessions 1-3.  I haven't watched it yet so I don't know anything much but I did put the third disc(which said session 3) in the dvd player and it showed episode 22-26 or something along that line.  Well, I was getting confused.  So, I got on e-bay and found where someone was selling Session 4 by itself and it said it contained episodes 15-18.  So, my question is...is The Perfect Sessions dvd contain the whole series?  Every episode?