I’ve been shopping at Costco for decades, and I’ll admit it took me years to notice that the price signs were talking to me.

They are. The last few cents of a price, plus a tiny star in the corner, can tell you whether you’re paying full freight, getting a markdown or looking at your last chance to buy something you love.

Costco doesn’t advertise any of this. Back in 2014, the company’s then-CFO, Richard Galanti, told Reuters the codes exist but are meant to help employees move merchandise. In his words, “It’s not any sort of secret agent stuff.”

Fair enough. But that doesn’t mean you can’t use it. Here’s how.

Start with the star

If you learn only one code, make it this one: a small asterisk in the upper-right corner of the price sign.

It means the store isn’t reordering that item. When it’s gone, it’s gone. Some shoppers call it the death star, and if it shows up on something you buy all the time, that’s your cue to stock up.

It’s also why so many people are surprised when a favorite vanishes. But the warning was right there on the sign.

Then read the cents

Here’s the catch: Nobody outside Costco has an official decoder, and shoppers and bloggers don’t all agree on the details. Codes can vary from warehouse to warehouse, too. So treat these as strong clues, not guarantees.

• .99: Regular price. No discount, but the item will probably be around next time.
• .97: Marked down. This is the ending most bargain hunters look for. If you also see the star, the store is clearing it out for good.
• .00 or .88: A markdown set by the store itself, often to clear a few leftovers. These can be the lowest prices in the building, but they can also mark a returned item or a floor model. Look it over before it goes in your cart.
• Other odd endings, such as .49 or .79: Often a temporary deal from the manufacturer. Fine to buy, but not a closeout.

My rule of thumb: The star tells you how long you have. The cents tell you how good the price is. A star plus .97 is the strongest buy signal on the floor.

The staff lingo you might overhear

Costco employees have their own vocabulary too. Most of it won’t save you money, but a few terms are worth knowing.

• Action alley: The wide main aisle where seasonal goods, TVs and promotions land. Stuff moves fast here, so it’s worth a walk-through every visit.
• The fence: The fenced area near the entrance that holds seasonal items, like pool gear in summer and decorations in fall.
• Go-backs: Items shoppers changed their minds about and left at the registers. Workers wheel them back to the shelves.
• DNI: Short for “do not inventory.” You may see it scrawled on a box. It usually marks goods headed back to the supplier.
• Code 99: An overhead page you hope you never hear. It calls staff to a safety or security problem.

One more money move: Watch the price after you buy

Here’s the tip I’d put ahead of every code on this list. Costco says that if the price of something you bought drops within 30 days, you can ask for the difference back.

That’s no small thing on a TV, a mattress or a set of tires. Bring your receipt or membership card to the returns counter for warehouse purchases, or use the request form in your online account for Costco.com orders.

Just know that warehouse and online prices are separate. You can’t claim a lower online price on something you bought in the store, or the other way around.

Bottom line

Look for the star when you care about an item. Look at the cents when you care about the price. And keep your receipt for 30 days.

None of it is secret agent stuff. But it’s real money.