Style guide. Sounds like the one my work uses (Associated Press):

- Numbers up to ten are written as words

- Numbers 11 and higher are numerals

- Any number that starts a sentence is written as a word

What does your style guide say about periods? I notice none of your bullets ended with a period. As a programmer I often struggle with whether I should end my comment with a period.

First, I dislike the AP style guide. So my own writing will sometimes violate it just to please me.

As for periods, any phrase that is a complete sentence must have a final punctuation mark. So my bullet points would've required periods in a report. They also could've been connected by semicolons with a conjuction at the end of the second-to-last point:

- A;

- B; or

- C.

The idea is to stick to proper English sentences. The bullet points are just incidental formatting.

Answer the following: Does the period help in any way? Go from there.

This is the correct answer.

Style rules often look like: spell out any number under twelve (sometimes twenty), and spell out any number that starts a sentence. If you're unlucky, that can get you sentences like the above.

Seems to be a style that doesn't add anything useful.

In related news, a formal convention that really grates is the american way of spelling out a number then putting it in brackets after: "You are permitted fourteen (14) days holiday a year" kind of thing. If anyone can shed any light on that I'd be interested.

Oh I actually might know the answer to that one! According to my Commercial Paper professor it was an early way to prevent fraud and mutual mistake. It’s fairly easy to sneak an extra zero on the end of a written number or to transpose two numbers without anyone noticing. Checks still do this: “Pay twenty and xx/100 dollars” followed by “$20.00”

In theory if the written number doesn’t match the numeral the teller shouldn’t accept the check.

I'm not sure about other fields, but in Neuroscience we were taught to follow APA guidelines in our undergrad research fundamentals class. The APA style guide is very specific about things like when to spell out numbers, etc.

If I had to guess given the journal where it was published, I'd say it is for formatting purposes (better distribution of the words in the line).

Edit: reading the other comments, beginning vs non-beginning of a sentence also make sense.