where "A" is the symbol for the quantity, {"A"} symbolizes the numerical value of "A", and ["A"] represents the corresponding unit in which "A" is expressed here. Both the numerical value and the unit symbol are factors, and their product is the quantity. A quantity itself has no inherent particular numerical value or unit; as with any product, there are many different combinations of numerical value and unit that lead to the same quantity (e.g., "A" = 300 ⋅ m = 0.3 ⋅ km = ...). This ambiguity makes the {"A"} and ["A"] notations useless, unless they are used together.