Numbers and percentages
Generally speaking, 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, follow The Chicago Manual of Style, 16th 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 FreeStyle or 6 steps to better templates. This promotes ease of reading and scannability. In titles and headings, it's easier for users to scan numerals than it is for them to scan spelled-out numbers.
Use the full, four-digit year. For informal writing, it's okay to use an abbreviated form. For example, We're thankful technology isn't stuck in the '90s!
Do not use a short date format such as 10/2/19. In the US we read that as October 2, 2019. In other parts of the world, it is 10 February 2019.
Spell out percent in most cases. However, use the percent sign (%) in these cases to improve content scannability and allow users to digest the content more quickly:
- Tables 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.