How many shots do you think were drunk between these two pics?

I bought my boyfriend a fifth and figured we’d split it. He has a habit of going over half, so as I was heading to bed I made him promise he wouldn’t drink any of my half. I took a picture because I had a feeling he might drink it. And, behold, the level had gone down. I confronted him about breaking his promise and he says it was “just one shot”. It looks like more than just one to me though, so I thought I’d bring it up with some folks who may have more experience than I. Does this look like just one shot worth?