How can my Average Time on Site be that different between a table and a Key Metric Summary?

Good morning,
Recently I’ve been trying to make a deep dive on the Time on Site users spend on my web and I noticed that I have a very big difference between the Time on Site we see on the Freeform table for All visits, and the time we see in the the Key Metric Summary, even though we have the same filters applied.
I can tell it’s because of the days average but I would need you as experts to help me understand:
- Why such a big difference
- The meaning of each KPI
Thank you in advance!