XLMOD:02258 has malformed spaceLength value

[mobiusklein]

[Term]
id: XLMOD:02258
name: PhoX
def: "PhoX cross-linker." [PMID:31477730]
property_value: reactionSites: "2" xsd:nonNegativeInteger
property_value: spacerLength: "5.0-20.0" xsd:float  <<< Problem Here
is_a: XLMOD:00005 ! homofunctional cross-linker
relationship: has_handle XLMOD:00173 ! phosphonic acid
relationship: has_reactive_group XLMOD:00101 ! NHS ester

The spaceLength property value "5.0-20.0" does not comply with xsd:float. Is there an appropriate type for this expression "built-in"? If not, how are they declared/defined?