Replace spelled-out numbers with their digit equivalents, since the digits are easier to read and faster to understand:
INCORRECT: They issue between seven and twelve permits per year.
CORRECT: They issue between 7 and 12 permits per year.
Exception: If the number begins a sentence or otherwise reads awkwardly:
INCORRECT: 28 of our students attended.
CORRECT: Twenty-eight of our students attended.
CORRECT: In attendance were 28 of our students.
INCORRECT: In attendance were twenty-eight of our students.
INCORRECT: She is truly 1 of a kind.
CORRECT: She is truly one of a kind.
Go To: Usage Details or Content Style or Style Guide