2.1.1700 Part 1 Section, supHide (Hide Superscript (n-ary))

a.   The standard says that if supHide is omitted the lower limit will appear.

In Word, if supHide is omitted, the upper limit will appear.

b.   The standard allows supHide to be set when the upper limit is not empty.

In Word, if the supHide attribute is on while the upper limit of the n-ary function is not empty, the application will display this argument next to the base argument of the n-ary function.