Facebook ads using only Instagram.

Hi, so I created an ad. I remember seeing where I wanted my ad displayed and it had picked by default all of the options such as mobile news feed, desktop news feed, sidebar, and Instagram. I have gotten a lot of post engagements, but when I looked tonight in my ads manager and clicked on the placement tab, 100% of my ads have been shown and engaged on Instagram. That doesn't seem right. I feel like I'm missing out on a lot since it's apparantly not using facebook at all. Any ideas? I can't seem to go back and change that.