Is tipping $1 on a $12 takeout sandwich a nice gesture, or am I just insulting the staff?

I pick up a sandwich from the same local spot a few times a week. I see the staff all the time and they're cool, so I want to be nice. But the iPad screen defaults start at 20%-25%, which feels insane for a counter pickup where they just hand me a bag.

If I manually change it to $1, is that actually seen as a good gesture? Or does hitting a custom amount to leave a buck feel worse just hitting "no tip"?