Subtractive notation places one smaller power-of-ten symbol before the next two values: I before V or X, X before L or C, and C before D or M. That gives exactly six canonical pairs.
Six pairs cover the decimal places
IV and IX cover ones, XL and XC cover tens, and CD and CM cover hundreds. Thousands use repeated M only within the supported range.
Readable subtraction is not automatically canonical
A permissive right-to-left reading can assign 49 to IL, but the profile writes 49 as XLIX. RomanClear exposes the provisional value and suggestion rather than silently normalizing the source.
Verify the receiving convention
RomanClear uses the explicit modern 1–3,999 profile shown on every result. Historical inscriptions, clock faces, editorial house styles and organization-specific conventions may use other forms. Compare important output with the convention required by the document or system that will receive it.