Additional HSA contributions in 2023 for 2022

TurboTax asks if you contributed to an HSA in 2022. I wanted to confirm you can contribute in 2023 before tax day in April and have it count for 2022? 

When I add the maximum contribution of $7,300, TurboTax only reduces the tax owed by 1500. It goes from 19,500 to 18,000. What would be the reason for this small reduction? I was hoping to reduce adjusted gross income.