Almost entirely specific to commercials for diet products, this is the usual Unreadable Disclaimer
shown at the bottom of the screen when an ecstatic (and genuine) customer endorses the product by proudly stating "I lost 60 pounds!" What you're not told is that this particular customer was a fanatic about losing weight and pushed herself far harder than the average schlump would, thus losing twice or more what the plan or product really promises. The UK equivalent is "As part of a calorie controlled diet"; this is occasionally spoken by a reassuring female voice, but not usually.
This is also a part of infomercials touting real estate or stock market tricks. As satisfied customers testify to the massive amounts of money they made in ridiculously short periods of time, this disclaimer would be shown under them in virtually unreadable small print.
Also a staple of commercials advertising "multi-level marketing" pyramid schemes. Obviously a few people at the top of the pyramid will profit from "working at home", but the vast majority will lose most if not all of their investment.
Disturbingly, it's even appeared in commercials for a chain of private cancer clinics. The implication is, despite the heartwarming, soft-focus testimonial from the patient other doctors had given up on, most people told they have fatal cancer will, in fact, die from it — but give us your money anyway!
Car ads used to say "Your mileage (fuel consumption) may vary", until people stopped caring about gas mileage in The Nineties
. It's back now, in the fine print
about which specific EPA mileage tests were used and how it might not reflect your driving habits.