Goal conversion rate question

I would like to know how the goal conversion rate is calculated.

In the demo site, I see the definition of goal conversion rate is session with a complete goal/session, and I use unique goal conversions or goal conversions / total session, none of the results are equal to goal conversion rate.

Could you please help me to understand how this goal conversion rate calculates?

Goal conversion nor unique goal conversions aren’t in the equation. It’s the number of sessions with a goal conversion. It means that if in the session there were multiple conversions on different goals, it will be counted once.
To check what’s the number of sessions with conversion(s), create a flat table with Sessions metric and filter: Goal conversions in session > 0.