Set point and Set back

How is defult Honeybee’s setback schedule being calculated?

And if I choose 20 degrees as a setpoint of heating, how can I calculate Setback?

These values are being “assigned” and not “calculated”. These values are assigned based on the program (in your case office).

So How can I found setbacks for an office room in Iran for example?

You have to look into the local standards and see what do they suggest for setback during different seasons.

There is no local standard.
I myself should calculate setback, and I dont know how can I calculate.