A French standard sets out the principles for writing numbers, quantities, units, and symbols.

How do you write "two" as a number? Usually, with the Arabic numeral "2." Few of you use the Roman numeral "II." How do you symbolize addition? Commonly with the "+" sign. In everyday life, we write numbers, quantities (for example, the common name Celsius or the symbol Ω for Omega), and units (V for volt) according to common writing rules. These essential rules are set out in standard NF X02-003.

This French standard provides a comprehensive grammar for numbers, quantities, units, and symbols. In particular, it sets out the general principles for writing whole numbers, decimals, fractions, and mathematical symbols. Thus, using a comma to symbolize the decimal point or using the "-" sign to express a negative value is not a matter of chance, but rather a common rule of writing.
All the information needed to round numbers correctly is specified in the appendix to the standard.

Numbers, operation signs, quantities and symbols, units... The French standard brings together all the rules for writing so that everyone can write this data correctly.
It is a useful reference document for scientific and technical ratings.