In the Instagram Engagement section, after you turn on Enable IG Engagement and choose the Instagram Account, you can select: Everyone who engaged, Visited the profile, Engaged with posts, Sent a message, Saved posts and Profile followers. Each selected type is combined with the selected Retention Periods, creating one audience per period (for example, 7, 30 and 90 day engagement). The exception is Profile followers, which is always a single audience of all followers, with no period. There's also the Add @instagram to audience name option, which appends the profile's @ to the end of the name. It's useful when you manage multiple profiles in the same account.