What is Velocity?

Good afternoon,

I have a doubt about something that is explained in the Physics course.

Specifically, one example says:

For example, if you drive to a store and return home in half an hour and your car’s odometer shows the total distance traveled was 6 km, then your average speed was 12 km/h.

But, where does 12 come out from?? Even the picture underneath this example shows the 3 Km towards the shop and the 3 Km from the shop back to home. So, where does 12Km come from?

This also leads me to the same doubt when they show me the graph of the Velocity Vs Time: why both Instant Velocities (towards to shop and from the shop back home) are 12km/h each??

Thank you in advance

Daniel Rossi