google cloud platform – Why am I being charged for Vertex AI API usage when my Colab notebook is idle?

I have a Colab Enterprise .ipynb notebook (174KB) that hasn’t been run or edited in about a week—no active sessions, and it’s not tied to any schedules. According to the “Enabled API & Services” traffic report, there has been no traffic from Vertex AI. However, I’m being charged exactly 63p per day.

Is this normal? Does Google charge for simply having the Vertex AI API enabled? I did have a custom Runtime Template set up (now deleted), but since it wasn’t being actively used, I don’t think it would be causing charges.