Answer: Frequency
Explanation: In simple words, frequency refers to the number of times a unit repeat itself in a specified time period or as in the given sample base.
In the given case, the company wants to advertise their product in a limited area as often as possible. Hence they wants their promotional ads to repeat often so that they can reach to wider customer base or maximum people who go through that area witness those ads.
Hence they were concerned about the frequency as they wanted to the add to repeat as much as possible.