Facebook gives you 4 platforms where you can run your ad: Facebook (of course), Instagram, Messenger, and Audience Network.
By default, you will be advertising in all of them, but how do you know when to keep or remove one?
Unless you have a strong reason for keeping Instagram and not Facebook (I can’t think of any), the short answer is: look at the numbers.
The numbers above are for the past 7 days. Facebook drove the majority of the volume; the cheapest cost per result came from the Audience Network.
If there is no reason for keeping Instagram, you should remove it. It generated a weak volume at a high cost per result.
If you are not so sure about it, create a new campaign, same audience, targeting only Instagram users, and watch the numbers. Run it for seven days; if you are still getting poor numbers, then you know what to do.