Lol hard disagree, my friend. That tiny shelf sounds like a happy accident. Now you have a perfect spot for that one special teacup, and honestly that's a way funnier story than if it had worked right. Some of my best projects came from exactly that kind of measuring chaos.
Get what @derek78 is saying. I've messed up cuts before and just added a back panel to make it look planned. You could always stain it a different color to stand out. What are you putting on your tiny shelf?
Honestly I used to get so mad when my cuts were off. Like I'd start over every time. But last month I messed up a bookcase and just went with it, ended up with this weird little cubby that fits my router perfectly. Kinda changed how I see these things now.