Here:
https://dev.twitter.com/ads/reference/post/accounts/%3Aaccount_id/campaigns
requency_cap
optional
An integer representing the number of times for which one user could be delivered an ad to.
Example Values: 5
duration_in_days
optional
An integer representing the time period within which the frequency_cap frequency is achieved. Only supports values of: 1, 7 and 30.
Example Values: 30
I think you should have an special feature activated. If it’s needed, you should talk with your ads account manager (nothing related with API, I guess)
Thanks