FaceTime on my MacBook
Facetime is a 1:1 system. So, you can only be connected to 1 person. It's more likely the app had gotten run as bassplayer7 suggested and the green light just indicated that your camera was in use by an application. The 9 may have referred to the number of people in your address book you can Facetime with or that there are 9 recents in the recents list.