This summary is not the rule. The rule text controls.
This rule explains how the bar association decides where a member officially lives for its own record-keeping purposes. Instead of looking at where you actually live day to day, the association simply checks the mailing address you have on file to receive the Association's Journal (its official publication).
Whatever county that mailing address is in becomes your county of residence under these bylaws. This matters because other bylaws may use county residence to decide things like voting districts, local bar association assignments, or eligibility for certain positions within the organization.
If you want your official residence to reflect a different county, you would need to update the mailing address on file for your Journal subscription. Keeping this address current ensures the association has accurate information about where you are considered a resident for its internal purposes.