Where are the scale values in Odometry_pulisher.cpp come from?

[max90727]

Hi:
I am going to write the code to control the mecanum bot we just built and your project inspired me on how to control it. Thank you very much.
But I have a question when I look through your code.
In the file odometry_publisher, you load the parameters in the constructor with the default values. I want to know where are the values 2.15 and 2.7 come from.
Thank you
Best Regards