What principal address t o use for California state tax filing?

I moved to a new home within a different county, lets call it County A in California last year September. Before that I was lived for rest of the year in the same house in another county, call it County B, so for majority of 2020 I lived in County B. I currently live in County A. Which county should I choose as county of principal residence now that I am filing my state tax for California?

 

The TT Learn More comment on this is confusing: "Enter the county where you have your principal/physical residence on the date that you file your Form 540. If you reside in a foreign country at the time of filing, leave the county field blank. The home that you used the majority of the time during the year is considered your principal residence for that year."