MacBook Calendar App: Can't click and drag calendar from top of list

I've synced my Google Calendar with my Calendar app on my MacBook. I clicked and dragged the names of my calendars so as to order them as I please, but I can't move "2) AP Literature" from the top of the list. On my actual Google Calendar, the order is exactly as it should be.

Does anybody know why I can't click and drag "2) AP Literature" and/or how to ***** this problem?

Thanks in advance!

Calendar App

Google Calendar