Plurals

Don't use apostrophes to form plurals of proper nouns, acronyms, and numerals. For example, the plural of FAQ is FAQs, not FAQ's.
Don't pluralize single letters, symbols, or mathematical signs by adding an apostrophe and an s.
- Incorrect: Salesforce replaces unrecognizable characters with @’s.
- Correct: Salesforce replaces unrecognizable characters with the at (@) sign.
To form the plural of a numeral, add s but no apostrophe: Type three 2s.
In abbreviations for measurements, don't add an s to indicate plurality. For example: 10 oz or 30 mm.

Salesforce.com Style Guide for Documentation and User Interface Text