Gravity Analog TDS Sensor Coefficients

I am a student currently developing a water quality sensor for a project. I have purchased your TDS and temperature sensor to get a general idea on how it works. Everything turned out to work perfectly fine, as I used a more expensive TDS sensor as a reference point and the output values were quite similar. When looking into the code however, I saw that once the analog reading was converted into a voltage value, to convert the value into Electrical Conductivity, you used the following formula:
(133.42V^3 – 255.86V^2 + 857.39V)*KValue
I am very curious as to how you guys obtained these coefficients as I have looked every where and cannot find the reasoning. Can you tell me how you got these coefficients for this cubic polynomial?
Thank you and kind regards
Maybe they derived the equation from the characteristic curves of CD4060BM and LMV324. I personally used this sensor.

Thanks for the reply,
This is a possibility. Can you explain how you got this idea? The sensor uses this counter so I looked into the characteristics of the CD4060BM in the datasheet but couldn't find related values. I also sent them an email because I want to understand how they got to these values.
Thanks again.