Tested in French, but likely relevant for other languages: the regular expression for the detection of NumberPlusUnit in metadata.csv contains a list of special characters, such as % and ‰.
For NumberPlusUnit with %, value and unit are both assigned:
attr type="measurement" literal="2,3%." token="2,3%." value="2,3" unit="%"
For NumberPlusUnit with ‰, only value is assigned:
attr type="measurement" literal="2,3‰." token="2,3‰." value="2,3‰"