Hey @Alex_Flom
Essentially, in order for any Tailored Audiences to be targetable, the audience needs to have at least 500 matched members (i.e., members in the Audience that have corresponding Twitter accounts). So, even if the Audience is resized, as long as it has at least 500 members within it, it will be targetable. The reasons for this are mainly privacy related, since we don’t want to give advertisers the ability to infer the specific users being targeted, and therefore there is no way around this limit.
When you talk about Dynamic Ads, are you referring to the single_web_event_tags and/or UWT ?
Thanks!