I know Culture contributes to both border growth and progress toward the current civic. I believe only Culture generated by each city contributes to border growth, while civic progress is civilization wide. What I'm not clear on is whether culture contributes to both, or if one subtracts from the other. (Similar to food being eaten by citizens and only surplus food contributing to population growth.) Is some portion of the culture generated by a city consumed by border growth and only "excess culture" going toward civics?