I am new to straight razors and bought a Dovo Col Ichabod Conk 6/8 razor set Amazon.com: DOVO 506B 6/8 Col Conk Straight Razor with Full Shaving Set: Health & Personal Care

I see from reading beginners posts that it seems that most beginners start with the 5/8. What is the difference between the two and what are the benefits/downfalls? How are these measured, is it the width of the blade? Would it be better for me to buy a 5/8 since I am a beginner? Overall I like the razor itself but am unhappy with the set. I obviously paid too much as the brush is garbage and the case is plastic. I figured for that price the accessories would be a little higher quality. Overall though I am totally hooked! I can see that I am going to spend a fortune as time passes. Thanks for all the help.