How does an E6 have 6 service stripes?

Not so difficult to figure out. You're guessing at the uniform without knowing anything about the soldier.
I have served in the Women's Army Corp, the USAR, the ARNG, in the Regular Army and in the Retired Reserve. My total years of service equals 34. I wear 10 service stripes on my E6 uniform, which you would know nothing about without inquiring. Be careful how you inquire.
FYI, I was promoted to E-7(T) on the condition of completion of ANOC. Unfortunately, my age interfered as I was retired at age 60 before I was able to attend the course as all classes had been filled.

My husband retired with 22 years as a SSG.

Inappropriate uniform so many errors

It happens. There was a SSG I knew in a band unit in the National Guard with 10 service stripes for 30yrs. I’m a SSG myself with 7 for 21 years for a variety of reasons.

I retired with 7 service stripes 21 years as an E-5 SGT. There is several reasons that can contribute to this. He was probably Grandfathered in when the Retention in Service and Grade policy was introduced. If you didn't make the next pay grade in the required time, then you was discharge. Another reason he could have been reduced in rank when he already had 18 years in but the sentence wasn't sever enough to warrant jail time or discharge. Remember that back in the day, it wasn't heard of for E-3 or E-4 to retire with 20 + years of service.

Dah! Prior service.

Why does it matter? He must have earned them.

Thank him for his service and move on

Reservists don't high year tenure so you could feasibly retire as an E4. LOL

Not saying this guy is but we do wear the same uniforms as regular component.

Because not everyone gets advanced as quickly as you have. Doesn’t make them any less of a soldier. I personally think they promote people too quickly these days