The assessed value is supposed to be 70% of fair market value:

"The 2022 revaluation of all real estate in the City of Stamford is complete. As per the General Statutes of the State of Connecticut (§12-55 & §12-62(f) and local ordinance property assessment notices were recently mailed to all property owners. The new assessment represents 70% of the estimated fair market value as of October 1, 2022. The last revaluation was performed as of October 1, 2017."

https://www.stamfordct.gov/government/administration/property-assessment/property-revaluation

I believe an appeal is far more likely to lower your assessment than to raise it, so you'd have little to lose. I couldn't tell you the proper documentation to help your case, but the recent assessment and the comps sound like they would improve your case.