It’s currently possible to target more than one age bucket for a given line item through the Ads API. As early as 2018-04-03, it will only be possible to target a single age bucket per line item.
We’re making this change in order to be consistent with ads.twitter.com and because the existing age bucket ranges cover most advertiser use cases.
Please update your targeting logic before this change takes place.
Twitter Ads API Team
Related: Announcement: Age targeting GA