Numerals or No?

Latent Print presents Styleguide Wednesday, a post each Wednesday featuring an editorial convention from the world of styleguides. View previous Latent Print moments of stylebook study and reflection here. This week features numbers in a range, numerals or no?

AP conventionalists tend to spell out single-digit numerals. But the convention becomes wonky in the following example: Run the water from 30 seconds to two minutes.
Consulting Chicago, immediately following their coverage of the AP convention, we find verse 9.7: “Where many numbers occur within a paragraph or a series of paragraphs, maintain consistency in the immediate context. If according to rule you must use numerals for one of the numbers in a given category, use them for all in that category.”
Further, Chicago’s treatment of numerals in ranges, 9.63, shows figures consistently or spellings consistently in the examples.
Paragraph 436a in Greggs reads, “Use figures (even from 1 through 10) to express periods of time.”
The sentence becomes Run the water from 30 seconds to 2 minutes.

Numbers style demands flexibility from the copy editor. Where consistency is key, apply it. But, "Consistency must sometimes give way to readability," Chicago 9.1 warns.
In today's example consistent numerals is a likely improvement. Near deadline you’d succeed leaving the expression as is. The subject might not enthuse the boss; come to Latent Print to discuss nuances of number consistency.