Surely correct unit associated with IfcIonConcentrationUnit?

The documentation of [IfcIonConcentrationMeasure](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC1/HTML/link/ifcionconcentrationmeasure.htm) says the unit is mg/L, however in the [overview](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC1/HTML/schema/ifcmeasureresource/content.htm), the unit is g/L. Any other source I consult on the Web seems to use PPM or count/volume (volume as M^3, L, mL, NanoL).

QUDT knows [IonDensity](https://qudt.org/vocab/quantitykind/IonDensity) (aka IonConcentration) as number of ions per unit volume, apparently as defined by paywalled [ISO 80000-10:2019](https://www.iso.org/standard/64980.html).