QtCharts: Qml ValueAxis labelFormat online documentation vs offline docs mismatch

In the documentation here:

https://doc.qt.io/qt-5/qml-qtcharts-valueaxis.html#labelFormat-prop

labelFormat is documented as a string.

However, with the documentation included with prebuilt binaries for 5.15.5 msvc2019 x64 the type is documented as a real as seen in the attached image.