I couldn't stand it anymore. I called the store, talked to Marcie in Customer Service, and got the answer.
First I softened her up by telling her I had a strange question that I just had to have answered. She seemed a little wary, but willing to help. I described the tuna signs: "Do not bluff canned tuna." She told me they were internal signs for the stock crew.
Well, yeah, I kind of got that part, but I didn't say that! I just asked a follow-up question. "What do they mean???"
That made her laugh. I think she finally understood how strange they looked if you didn't know what "bluff" meant. She very kindly explained that "bluff" in this context means to pull everything to the front of the shelf. You know, to neaten it up.
Many, many years ago--when I worked at Walgreen's one summer--this was called "facing" and it was my favorite part of the job. Way more fun than running the register. Mind you, this was back in the days before scanning, when you had to know the prices and also know what was on sale. Preferably before you rang the item up wrong and got corrected by the customer. I think I was the Queen of the Overrings. Did I mention that I didn't especially enjoy that job?
Anyway, Marcie was not so forthcoming about the purpose of the signs, other than to communicate with the stock crew. I wonder if someone is in trouble and they want the shelves to stay just as they are until that person returns, so they can see what they failed to do? Whatever the reason, Marcie didn't want to talk about that part.
She warmed up to my gratitude, though, because in response to my thank you, she said that now when I start working at Publix, I'll be a star because I'll already know something on my first day on the job.
I'm not sure I want to envision a future at Publix--I suspect it wouldn't pay enough to cover my massive student loan payments--but it's nice to know I'm prepared, just in case.