The UCUM page should add a section like this:

Curly-braces codes

UCUM supports adding curly-braces in the 'code' element to allow additional human-readable content.   E.g. 3 "{cartons}".  In FHIR, the Quantity.unit and Coding.display are typically available to convey a human-readable unit and therefore there is less need for using curly-braces in the Quantity.code element.  Because some systems may not recognize that codes containing distinct curly-brace content are in fact equivalent, it is recommended that use of curly-braced content be minimized and the human-readable representation be sent in those elements specifically for that purpose.