On https://schema.org/termDuration, there is...

The amount of time in a term as defined by the institution. A term is a length of time where students take one or more classes. Semesters and quarters are common units for term.

(emphasis mine), however the page goes on to say that the expected value type is Duration which uses the ISO-8601 duration format.

ISO-8601 doesn't have provisions for semesters or quarters.

Can this property documentation be clarified?