Numbers and percentages
Numbers
Generally speaking, I follow the guidelines outlined in the Microsoft
Manual of Style, Fourth Edition However, if the document is for a more
general audience and isn't primarily instruction, I follow The Chicago
Manual of Style, 18th edition
In body copy, spell out numbers zero through nine, and use numerals for numbers 10 and greater. This is true of ordinal numbers, as well. Spell out first to ninth, and then use 10th or greater.
In titles, subheadings, and interface labels, use numerals instead of spelling out numbers. For example, 10 tips for using URLs or 6 steps to better footnotes. This promotes ease of reading and scannability. In titles and headings, it's easier for readers to scan numerals than it is for them to scan written-out numbers.
Dates
Use the full, four-digit year unless you're writing something more informal. Then it's okay to use an abbreviated form. For example, We're thankful printing technology isn't stuck in the '80s!
Do not use date abbreviations such as 10/2/19. In the USÂ we read that as October 2, 2019. In other parts of the world, it is 10 February 2019.
Percentages
Spell out percent in most cases. However, you can use the percent sign (%) in these cases to help the reader scan and understand easier:
- Tables and in technical or scientific writing For example: If the progress meter sits at 60% or lower for more than 20 minutes, close the program and start again.
- Headings and subheadings For example: Clearing 100% of all errors.
- Interface labels. 50% saturation
- Captions. Preview shows how your changes look before you save.