results question

I am an American, so I didn't grow up with soccer like a lot of people on here, so my knowledge is somewhat limited. I have a question about season standings. I the champions league. We are in group round 6, and three teams in my group have 4 wins and 2 losses, I have the most GF with 18 (they have 12 and 11) and GA I have 6, they each have 7. PT is 12 for everyone. My question is, why am I third?

As far as I understand, you should be in 1st place, as your Goal Differential is 12, while theirs are 5 and 4.