Sometimes numbers are easier to process than words; sometimes, it's the other way around. The phrase "a quarter to nine" is more difficult to process than 8:45 AM. On the upside, if your dentist appointment is on September 3, and today is September 2, the simplest way to put it is, "My dentist appointment is tomorrow."

Microcopy isn't the text users want to see — it's the text that guides them to the content they actually want to see. User-friendly microcopy should have high readability so users can quickly scan the interface. The job of UX writers is, ideally, to decrease the general cognitive load. That means writing numbers in digits (5 instead of five).

Divide long strains of numbers into chunks. For example, use spacing or hyphens when writing phone or credit card numbers to make them easier to read.