Middle of Program But Need to Log Rest Day

I just wrenched my left shoulder blade moving the shepard’s hook that I hang my hummingbird feeder from. A weird way to strain myself, I know. I think my body is just tired.

Here’s my question: I’m in the middle of Erica’s 10 day challenge. Is it possible to mark today a day as a “rest day” in the middle of a program? I know I can make a note to myself and reschedule the workout but I’d like to see the gray line on my calendar. Thanks in advance for any help/advice!