Climate control question

[dane]

Okay this might sound dumb, but am a little confused,
correct me.

when i change the temperature controls on either the driver side or passenger the air changes cold or hot as set in the lower cabin, however I still get cold air from the airflow for the upper body. When i make a change with a serrated dial there it changes hot or cold.

so what is the purpose of this? why 2 seperate temperature controls for upper and lower cabin? am I doing something wrong?

I thought just by changing the main temp control it would control all,

thanks,

Dane.