The topic of when to write numbers out and when to use numerals concerns and confounds a lot of people.

America’s two most influential style and usage guides have different approaches: The Associated Press Stylebook recommends spelling out the numbers zero through nine and using numerals thereafter—until one million is reached. Here are four examples of how to write numbers above 999,999 in AP style: 1 million; 20 million; 20,040,086; 2.7 trillion.

The Chicago Manual of Style recommends spelling out the numbers zero through one hundred and using figures thereafter—except for whole numbers used in combination with hundred, thousand, hundred thousand, million, billion, and beyond (e.g., two hundred; twenty-eight thousand; three hundred thousand; one million). In Chicago style, as opposed to AP style, we would write four hundred, eight thousand, and twenty million with no numerals—but like AP, Chicago style would require numerals for 401; 8,012; and 20,040,086.

There are only a handful of rules for writing numbers that virtually everyone agrees on. Two major ones: Numbers beginning sentences must be written out (Eight thousand twelve people attended the concert). Years (8 B.C., 2015) are expressed in numerals. But spelling out numbers vs. using numerals mostly comes down to policies and preferences that vary from publisher to publisher.

The topic causes further confusion because exceptions to just about every rule or practice crop up constantly. For instance, She walked 3 miles; Add 4 teaspoons of salt; Timmy is 5 years old; and The car is 6 feet wide are all correct in AP style, despite contradicting AP’s own rule of spelling out numbers between zero and nine.

Chicago endorses the following sentence “for the sake of consistency”: A mixture of buildings—one of 103 stories, five of more than 50, and a dozen of only 3 or 4—has been suggested for the area. Chicago explains why it does not spell out 50, 3, and 4: “If according to rule you must use numerals for one of the numbers [103] in a given category, use them for all in that category.” But why, then, are one, five, and a dozen written out? Because “items in one category may be given as numerals and items in another spelled out.”

AP’s approach to numbers is far less nuanced than Chicago’s. This may be because the Associated Press Stylebook is targeted to newspapers and magazines, which toil in a world of deadlines. There simply isn’t time to get sidetracked by numerical niceties when your article is due in three hours.

Here is a sentence from a profile that appeared in a big-city newspaper: “He has delivered a tutorial about the First, Second, Fourth, Fifth, Sixth, Ninth and 10th amendments to the Constitution.” Note the glorious inconsistency of “10th,” which would make Chicago Manual of Style disciples apoplectic.

But AP style stipulates “10th,” not “Tenth,” and that’s that. It may look odd, but is the sentence not clear and unambiguous? When it comes to the arcane, convoluted subject of writing numbers, there’s something refreshing about AP’s streamlined approach.