How to count...
by Puddin'
As a writer, you're meant to put words on blank paper. Accountants, on the other hand, are paid to put arabic numbers on paper with lines on it, which makes all the difference. Arabic numbers are not words, they're symbols, which don't actually translate all that well into real words. There are a whole set of rules that are absolutely mandatory when writers write using numbers, mostly to avoid confusion, but also to avoid looking like a rank amateur. The two instantly diagnostic symptoms of amateur writing are bad spelling, and the inappropriate use of arabic numerals.
The first thing a writer has to know about arabic numbers is that they're not precise, even though they look like they ought to be, and it's usually important for a writer to get the words right all the time. If you write: "Sam said, ‘It's 7:00,’" what the heck did Sam actually say? "Seven?" "Seven o'clock?" "Sevenish?" "Seven on the dot?" "Seven exactly?" "Seven AM?" "Seven PM?"" "Seven in the early evening?" "Seven in the morning?" "Oh seven hundred military time?" Those bare arabic symbols say nothing at all beyond what an accountant might dream of, and leaving important details as an exercise for the reader is rarely a good idea.
Every professional writing venue has what's called a "style guide" which details many of the rules associated with putting words on paper for that particular venue. Newspapers have style guides, as do magazines, as do book publishers, as do many web sites. This article addresses only the use of numbers, and offers explanations, which is rather more than most style guides do, since the typical response to submissions which don't follow the rules is to toss them into the trash.
Number Styles
Rule One — Spell out every isolated single-digit whole number. Arabic numerals should be used for large numbers, exact times, exact amounts, and certain other specific situations, but the exact point at which numbers become “large” varies. Some venues treat ten as a large number, but see rule two.
Correct Examples: The two of us went to town. I have 10,763 unique clips in my paperclip collection.