Welcome!

+1 on Jockeys advise. The 4/8, 5/8 are units of measurement, as in the width of the blade; 4/8" (inches). Some like wider/heavier blades than others. It just seems to be personal preference. I am fairly new myself, and still enjoy my 6/8" Dovo special, but to each his own.

Good luck and happy shaving.