I am currently Active Army. I was looking at my ERB and some of my Prior Service Dates don't look correct. Am I missing something?

This is a job for your career counselor to fix. Technically, by regulation it falls on the S1, but career counselors are better trained for it.
Your DIEMS is the date of the very first contract you signed in 1993. When this is wrong it creates the issue that you can't update your schools and assignments on you ERB correctly because emilpo won't let you enter anything on the ERB that is prior to the DIEMS listed.

Your Pay Entry date is calculated by taking your guard time, plus the two years of IRR you should have had after (that should equal 8 years exactly because of Military Service Obligation), and subtracting it from the date you came back in.

Your BASD is calculated the same, except it's not your guard time, it's your AD time. You would add all the AT's, basic, AIT, and any deployments, then subtract that number of time from the day you came active.