Refining audience by geographic location

I see in the "refine your audience" section of the advance search ads page https://searchads.apple.com/advanced/

that it now lets you refine your audience to be based on geographic location. However, it appears to be either by city or state. Our app is a service based app, but our markets are much larger than a single city. I'm wondering, how much area surrounding the cities is covered by each one we select?
Does it limit it to the geographic bounds of the city? Or is there an X mile radius around the city?


How many cities can you choose?
This looks like a cool feature that enables us to benefit from search ads, being a location based service market place. On initial launch, we couldn't benefit from search ads because most of the audience would be outside of our service area, but we're interested in trying it out this coming Spring if we're able to simultaneously limit the geographic areas, and show the ads in enough of the geographic areas we operate in.