Numbers can be either spelled out (e.g. “Nine thousands”) or written in numerals (e.g. “9,000”). Be consistent.
In case multiple numbers follow each other, write the first in numerals and spell the second one out (e.g. “3 nine-inch boards”).
Use commas as separators (i.e. “10 thousand” = “10,000”).
Use full stops for decimals (e.g. “10.5”).
Only use numbers up to 99,999.
In the case of millions, billions, etc, said word needs to follow the number and present a space (e.g. “10 million”), but only when it comes to “round numbers” (e.g. “12 million” or “19 billion”).
