Do you write gym sets down or keep them in your head?

I’m not a real gym person, more of a 6 a.m. YMCA walker who wandered into the weight room. My pharmacy tech asked how I was feeling on the new refill, and I said stronger, but honestly I can’t remember if I did two sets or three of the seated row on Tuesday. I’ve been scribbling on the back of an insurance EOB that was already in my purse. It’s a mess. I want something simple: date, machine, weight, how it felt. Do you use a tiny notebook, a note on your phone, or just keep it in your head? I’m trying to see if my workouts are actually moving while the scale does its slow thing. Also, does your insurance or gym app give you anything useful, or is that just clutter?