Caught out by the FDA.
I happened to be in the bug spray section of the store when I spotted a bottle of mosquito repellant that proudly proclaimed "100%
But the FDA-mandated labelling tells a different story:
Similarly, foods labeled "zero fat" are actually allowed to contain up to a half gram of fat. (Well, up to but not including.) This is a definition of "zero" with which I had previously been unfamiliar.