Perhaps one of the greatest mysteries of Thanksgiving is the cranberry sauce — and we’re not talking about why people eat it: Why are the labels on Ocean Spray cans upside down? Observant consumers have noticed that the labels on jellied cranberry sauce cans are flipped, meaning the rounded edge that’s typically on the bottom of most canned goods is on top of Ocean Spray cranberry sauce cans. According to Ocean Spray, that’s intentional: It creates a seamless serving experience. The cans are “filled and labeled upside down with the rounded edge on top and the sharp can-like edge on the bottom to keep the jelly whole,” an Ocean Spray spokesperson told CNN Business. That creates an air bubble on the rounded side (a.k.a. the top) so customers can “swipe the edge of the can with a knife to break the vacuum and the log will easily slide out.” This process has been in use since the early 2000s. Adweek, which recently reported this important can caveat, noted that about 67 million cans are sold between Thanksgiving and Christmas. But like other Thanksgiving meal staples, canned cranberry sauce might be hard to come by. The sauce has 79% availability across national retailers, which is down from 89% in that same period, according to IRI, a market research firm that tracks US retail sales. Ocean Spray, a farmer co-operative that makes cranberry sauce and sells bagged cranberries, said that “consumers may experience some availability issues at times on a variety of cranberry products,” because of supply chain issues. The co-op noted that it doesn’t expect “significant impacts” on the availability of its products. – CNN Business’ Danielle Wiener-Bronner contributed to this report.