Ever wonder what your tip percentage means? Ever have a friend say, “I’m going to be generous and leave a little extra,” but then you just leave the requisite 15 percent, close your wallet, and walk out the door? Well, as a bartender and food-service worker most of my adult life, I am here to tell you what these numbers really mean to the industry.

Zero percent Ah, the soul-crushing blank spot on the credit-card receipt. Or worse, the handwritten Ø with the slash through it. Unfortunately you obviously disliked your experience. That, or you don’t care that people’s livelihoods are determined by tips (slow, year-by-year minimum-wage increases notwithstanding). Leaving no tip, especially on a big tab, pretty much ensures you won’t be coming back to the restaurant. OK, that’s fine. But the thing about life is we’ll likely see each other outside of the restaurant. And maybe you’ll be in need of help—a flat tire, rushing to a movie—and there we’ll be face-to-face again. I’ll probably help you anyway, but I’d have grounds not to.

Five to 10 percent Thankfully, you realize money still makes the world go ‘round and you’re not completely heartless. I understand that I forgot your extra hot water or your beer came really late and you wanted to make a statement. Something like “I’m in control here.” For a millisecond that will be true, and really that’s all that matters in a capital-driven, power-based human interaction. You’ll probably come back sometime in the next month or two with a smile, pretending nothing happened, saying, “Hey, buddy, can I get a Stella? Thanks.” And I’ll have to oblige because that’s how jobs work.

15 percent Standard, par for the course. You did all you had to. But you also don’t realize that an extra buck or two—or even five—would increase the likelihood of being noticed, or even endear you to the staff. Make a good impression, show the people around you that you understand how generosity works, and they will likely reciprocate. In a rush? Let me grab your check right away. Left your credit card at home? No problem, you can get us for that beer next time. A little generosity goes a long way.

20 to 30 percent What a joy it is to be around you! You understand that by being liberal with your tip, we can kind of forget money is a necessity and just be kind to each other. By being generous, you remove the barrier of economics, in a way, and the world thanks you.

50+ percent You’re a unicorn, the thing memories are made of. You’re the person who leaves a $100 bill on the table and wishes us Happy Holidays as you walk out. Not just because the extra money is helpful—I mean, think about it; on any given night, two or three bartenders could be working, plus you have to tip out the kitchen and the back of the house, so a $100 tip is really like $20 to each person working—but because you know how to show gratitude and offer joy. You’re a bright light in a world that can often feel thankless.

Bonus advice: 1) When splitting a tab and using cash, make sure the server knows some of that cash is going toward a tip. 2) If your tab is under $20, don’t split it! And stop tearing apart those damn coasters!