How does an E6 have 6 service stripes?

You answered your own question. Time in Service doesn't dictate your rank.

He does not possess an exemplary record, e.g., he got busted once or twice?

PFC, this isn't a smart question at all. Until you fully understand the Army and it's promotion structure you'll understand. With how the promotion is now that everyone has to go to NCOA in order to get promoted. Some soldiers like myself aren't book learners but is forced to learn that way. It's difficult for some than others. So until you actually grow up and understand I have to say that this is an ignorant question.

A better question would be, why do you have over a year time in service and 5 months time in grade and aren't an E4? Both are waiverable.

I had 9 stripes, bet then that was Nat'l Guard, at the dry cleaners at Ft Myer VA, I saw a Class A jacket SSG with 13 stripes, woo hoo, my hero

Private you know the military has been downsizing the last 5 years. This means few if any E-7 slots.

I made E6 in 8 yrs, busted to E5 at 11 yrs, made E6 again at 13 yrs, up for warrant selection then deployed 3 times, then 3 years in wounded warrior battalion. Retired with 20 yrs as an E6 and I was far from an underachiever. Honor graduate from Jumpmaster, 2nd in class at Pathfinder school, honor graduate in various other courses including a secondary MOS for a volunteer mission to Bosnia. Shit happens

He/ she served 18+ years. My retired uniform has 6. It also has 9 combat stripes.

A lot of negative comments about this NCO. Did anyone see the 8 combat stripes? Or are you just focused on a SSG with 18 yrs and the 6 Service Stripes? As stated, he is an AIT platoon Sergeant so he must be squared away as they do not last long in that position if they aren't squared away. Some MOSs are hard to get promoted and many times not due to lack of effort. A SSG retiring at 20 is not uncommon at all.

The Army wasn't always like we know it. They didn't just give away stripes like they do now a days...