Adding a font.pixelSize propertychanges does not give the expected result

See attached file.

Adding this line does not give the expected result. All selected items seem to go to size 3 instead of adding +3.
PropertyChanges

{ target: itemText; font.pixelSize: font.pixelSize+3 }

But this line below works better except about the bug QTBUG-11110 :
PropertyChanges

{ target: itemText; font.pointSize: font.pointSize+3 }