The numbers on a toaster indicate duration of toasting in minutes, and not a "degree of toastiness."
A perennially popular image pops up with frequency on social media, claiming (to the surprise of users) that the dial on a toaster determines the duration of toasting in minutes and not a degree of “toasty-ness”:
The world has seemingly presumed that the “darkness” dial settings on toasters (typically a one-to-five range) show how toasted a slice of bread would be: Selection of a “1” would result in lightly browned bread with little crunch, and choosing “5” would produce a blackened, crunchy slice.
Like many online images of its type, this one seemingly appeared from nowhere and provided no context or information beyond a single statement, leaving viewers slightly less confident in their toasting prowess and unsure if they’d been using toasters correctly throughout their lives.
However, nearly all appliances (no matter how simple or minor) come with manuals. According to toaster manuals published by Cuisinart [PDF], DeLonghi [PDF], and Breville [PDF] (among others), the function of the “browning control” setting is consistent across brands, toasters, and continents:
Clearly, “big toast” maintains an industry-wide standard for toaster settings, and toaster dials or sliders indeed indicate levels of “toasty-ness” and are not timers that set the number of minutes bread is to be heated. Unless toaster manufacturers have a time-based scale that they keep entirely secret, toast lovers can rest assured knowing that their preferred settings are based on the darkness level of toast and not a less precise method of timing that might lead to inconsistent or unexpected results.